Browsing by Subject "lactic acid bacteria"

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  • Suhonen, Anniina (Helsingin yliopisto, 2019)
    Lactic acid bacteria have a long history of use in food industry due to their favorable metabolic properties and health benefits for human health. Therefore, they are generally recognized as safe (GRAS) by FDA (U.S Food and Drug Administration) and have QPS (Qualified Presumption of Safety) status granted by EFSA (European Food Safety Authority). Nowadays, antimicrobial resistance (AMR) is a serious global risk and due to the increasing AMRs, more and more microbial infections have become more difficult to treat with antibiotics. AMR has mainly been of concern in relation to pathogenic microbes. However, since fermented foods are favorable environments for AMR gene transfer it should also be considered in the context of beneficial bacteria and their potential to spread AMR genes into pathogenic microbes. The aim of this study was to determine antibiotic susceptibilities of Lactobacillus plantarum, Lactobacillus rhamnosus, Leuconostoc sp. and Weissella sp. strains by E-test method and to detect selected specific antibiotic resistance genes by PCR. In addition, the goal was to define new cut-off values for Weissella strains since, so far, these have not been defined by EFSA. Antibiotic susceptibilities were determined against eight antibiotics: ampicillin, chloramphenicol, clindamycin, erythromycin, gentamicin, kanamycin, streptomycin and tetracycline. The detected AMR genes were blaZ, mecA, cat, lnuA, tetK and tetM. Most of the determined strains were observed to exhibit a notable resistance to kanamycin. Several Leuconostoc sp. and L. rhamnosus strains showed also resistance to chloramphenicol. Interestingly, one L. rhamnosus strain was observed to exhibit multiresistance to chloramphenicol and clindamycin. Moreover, 48% Leuconostoc strains had higher MIC value for streptomycin than the cut-off value defined by EFSA. Any of the selected AMR genes were not detected even though a notable resistance during the phenotypic testing was observed. However, this might be explained by the small amount of detected AMR genes. The results obtained in the present study provided more information about the antibiotic susceptibility and the safety of L. plantarum, L. rhamnosus, Leuconostoc sp. and Weissella sp. strains. Moreover, new cut-off values were proposed for Weissella sp. strains.
  • Lyhs, Ulrike; Björkroth, Johanna; Korkeala, Hannu (Elsevier, 1999)
    A total of 405 lactic acid bacteria (LAB) isolated from spoiled, vacuum-packaged, salted, sodium nitrite- or potassium nitrate-treated, cold-smoked rainbow trout stored at 48C or 88C were characterised and identified using a molecular method. The isolates were initially classified according to their restriction endonuclease profiles using HindIII and EcoRI restriction endonucleases and further characterised by rRNA gene restriction patterns (ribotypes). Numerical analysis of these ribopatterns was performed together with 19 reference LAB strain patterns in order to identify the isolates to species level. The strains were divided with HindIII and EcoRI ribopatterns into ten and nine clusters at the similarity level of 65% and 50%, respectively. The Leuconostoc-clusters and the Lb. sakei /Lb. curvatus-clusters formed the two main groups. Only one isolate was identified as Lactobacillus plantarum and no Carnobacterium strains were discovered. For both enzymes, the 35 isolates possessing six individual ribotypes and forming five clusters could not be identified further with the reference strains used. The relative proportion of Leuconostoc mesenteroides subsp. mesenteroides was higher in all samples stored at 48C. Most of the Leuconostoc citreum were found in the samples stored at 88C, and particularly in the nitrite-treated samples.
  • Santos, Eva M.; Jaime, Isabel; Rovira, Jordi; Lyhs, Ulrike; Korkeala, Hannu; Björkroth, Johanna (Elsevier, 2005)
    A total of 176 lactic acid bacteria (LAB) isolated from a typical Spanish blood sausage called “morcilla de Burgos” were identified by means of phenotypic characteristics and 16S rDNA RFLP (ribotyping). LAB were isolated from “morcilla” of different producers and in different storage periods, that includes unpackaged, vacuum and modified atmosphere packaged “morcilla” and vacuum packed and pasteurised “morcilla”. The knowledge of specific spoilage bacteria of ”morcilla de Burgos” will be useful to design new preservation methods to extent the shelf-life of this product. Identification made according to phenotypic and biochemical characteristics shows the majority of the isolates were heterofermentative LAB (93.2%) and eight different bacterial groups could be distinguished (A-G). W. viridescens was the main species detected (42%). In addition, Leuconostoc spp. (23.9%), W. confusa (11.4%) and Lactobacillus fructosus (5.7%) species were found. Few strains were phenotypically missidentified as Lb. sanfrancisco, Pediococcus spp., Lb. sakei/curvatus and Carnobacterium spp. and 11 strains remained unknown. Most of the leuconostocs were identified as Lc. mesenteroides and Lc. carnosum species. Ribotyping shows a quite good correlation with phenotypic methods, although it has been possible to identify 15 different clusters. W. viridescens and leuconostocs were also the predominant LAB. Strains identified as W. confusa by phenotypic characteristics were resolved in W. confusa and W. cibaria by ribotyping. Neither Carnobacterium piscicola nor Lb. sanfrancisco were identified by means of genotypic method. All Lb. fructosus strains and some more included in different phenotypic groups (17 strains in total) could not be associated with any reference strain (cluster VII). Although some discrepancies exists the combination of phenotypic and genotypic methods led to a better identification and characterization of the strains isolated from “morcilla de Burgos”.
  • Peiponen, Susanna (Helsingfors universitet, 2008)
    Several canine clinical gastrointestinal problems, such as inflammatory bowel disease and small-intestinal bacterial overgrowth, are believed to be associated with bacteria. These conditions often lead to chronic diarrhea. Many canine gastrointestinal problems are treated with antibiotics, but due to increasing problems with antimicrobial resistance alternative therapies should be considered. One of these therapies is suggested be probiotic bacteria treatment, especially with members of the genus Lactobacillus due to their health-conferring properties. The probiotic characteristics of bacteria are linked to host specificity which is an important criterion for selection of a probiotic. Most of the commercial probiotic strains meant for dogs are not from canine origin. In addition many substances available in the Finnish market contain Enterococcus faecium, whose safety has been questioned due to it's pathogenic characteristics. This study was based on the study project investigating the effect of host-specific canine LAB on long term gastro-intestinal symptoms. The study was a randomized, double-blinded and placebo controlled trial. This study examined the changes in the canine faecal LAB microbiota caused by fed canine host-specific probiotic LAB. The purpose was to become familiar to the isolation of gastro-intestinal microbiota and to assess the potential alterations in the faeces by applicable methods. The most important methods were polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). During the study DGGE analysis proved to be a working method for analyzing bacterial communities. When the method becomes more familiar, it will probably be as common in use as agarose gel electrophoresis due to it's advantages. Some alterations of the microbiota could be seen on the DGGE analysis. During the experiment the bands resembling those of standard strains were dominant. This implies the Lactobacillus strains of interest being able to survive the canine intestine. However, after feeding seized the bands formed by the strains of interest disappeared and were replaced with bands of indigenous LAB. Also after the feeding seized, some new bands appeared on DGGE gel. This implies a contribution of fed probiotic mixture to the enhanced prevalence of potential novel microbes.
  • Halmemies-Beauchet-Filleau, Anni Ilona Karoliina; Shingfield, Kevin J; Heikkilä, Terttu; Kokkonen, Tuomo Juhani; Vanhatalo, Aila Orvokki; Jaakkola, Seija Liisa (Universität Bonn, 2018)
  • Viljanen, Janne (Helsingfors universitet, 2012)
    Exohomopolysaccharides (HOPS) are polysaccharides that are composed solely of glucose or fructose monomers and which are classified according to the linkage type between the monomers (e.g., dextran ?-[1?6]). Several different lactic acid bacteria (LAB) strains produce HOPS from sucrose. It is known that maltose can influence the synthesis of HOPS which can lead to formation of oligosaccharides. In fermented foods, HOPS and oligosaccharides can have both technological impact and prebiotic properties. The aim of this thesis was to investigate the synthesis of HOPS and oligosaccharides in mMRS broths and in oat bran gruel. Lactobacillus reuteri FUA 3048, Lb. reuteri LTH 5448, Weissella cibaria 10M and W. confusa DSM 20194 were used as starter cultures. HOPS and oligosaccharide yields in mMRS broths were analysed by ethanol precipitation and acid hydrolysis. An enzyme assisted method was used in order to quantify linear dextran content in freeze-dried oat gruels. Oligosaccharide profiles were analysed with high performance anion exchange chromatography with pulsed amperometric detetection. In mMRS broths, which contained 25 g/l sucrose (S-mMRS), LAB strains synthesised exosaccharides at concentrations of 0.9–2.3 g/l. Addition of maltose (34 g/l) significantly increased exosaccharide yield. This can be explained by strong malto-oligosaccharide (e.g., panose) synthesis. W. cibaria 10M produced 0.94 g/l linear dextran in S-mMRS broth and at 0.74 g/l in maltose containing broth and W. confusa DSM 20194 synthesised 1.7 g/l linear dextran in both broths. In oat gruel matrix (34 g/l maltose) W. confusa DSM 20194 synthesised 4.6 g/100 g dextran in freeze-dried gruel. In lower maltose concentrations dextran yield increased. Oligosaccharide profiles indicated that Weissella strains and the Lb. reuteri FUA 3048 strain synthesised gluco-oligosaccharides and Lb. reuteri LTH 5448 strain produced erlose. The results of this thesis give further insight in to role of maltose in HOPS synthesis in food matrices.
  • Koort, Joanna; Coenye, Tom; Vandamme, Peter; Sukura, Antti; Björkroth, Johanna (Society for General Microbiology, 2004)
    Isolates 302, 334, 356, 377 and 379, detected in modified atmosphere packaged (MAP) broiler meat, together with LMG 12317T and LMG 13617, detected in dog tonsils, were analysed in a polyphasic taxonomy study including numerical analysis of ribopatterns and whole cell protein patterns, 16S rDNA sequence analysis, DNA-DNA hybridisation and determination of some phenotypic properties. The results indicated that these isolates represent a new species in the genus Enterococcus. The isolates showed classical phenotypic reactions for the genus Enterococcus with the exception of not possessing the Lancefield group D antigen. Isolates 334, LMG 12317T, and LMG 13617 showed the highest 16S rDNA sequence similarity (98.3-99.0%) with the Enterococcus pallens type strain. In the distance matrix tree based on 16S rDNA sequences, the three isolates were located in the Enterococcus avium –group with E. pallens as their closest phylogenic neighbour. Numerical analyses of whole cell protein patterns and HindIII/EcoRI ribotypes placed all seven isolates together in a single cluster separated from the E. avium group reference strains. The DNA-DNA hybridisation level between strains 334 and LMG 12317T was 93.5% confirming that they represent the same species. Low hybridisation levels (12-30%) were, on the other hand, obtained with the E. pallens and Enterococcus raffinosus type strains. The name Enterococcus hermanniensis sp. nov. is proposed, with strain LMG 12317T (=CCUG 48100 T) as the type strain.
  • Björkroth, Johanna; Ristiniemi, Minna; Vandamme, Peter; Korkeala, Hannu (Elsevier, 2005)
    In order to show which of the initial lactic acid bacteria (LAB) contaminants are also causing spoilage of a modified-atmosphere-packaged (MAP), marinated broiler leg product at 6ºC, LAB were enumerated and identified on the 2nd and 17th day following manufacture. A total of 8 fresh and 13 spoiled packages were studied for LAB levels. In addition, aerobic mesophilic bacteria and Enterobacteriaceae were determined. The average CFU/g values in the 8 fresh packages were 1.3 × 103, 9.8 × 103 and 2.6 × 102 on de Man Rogosa Sharpe agar (MRS), Plate Count Agar (PCA) and Violet Red Bile Glucose agar (VRBG), respectively. The commercial shelf life for the product had been set as 12 days and all packages analyzed on the 17th day were deemed unfit for human consumption by the sensory analysis. The corresponding CFU/g averages in the spoiled product were 1.4 × 109, 1.1 × 109 and 3.9 × 107 on MRS, PCA and VRBG agar, respectively. For characterization of LAB population, 104 colonies originating from the fresh and 144 colonies from the spoiled packages were randomly picked, cultured pure and identified to species level using a 16 and 23S rDNA HindIII RFLP (ribotyping) database. The results showed that enterococci (35.7% of the LAB population) were dominating in the fresh product whereas carnobacteria (59.7%) dominated among the spoilage LAB. Enterococcus faecalis, Carnobacterium piscicola and Carnobacterium divergens were the main species detected. In general, when the initial LAB population is compared to the spoilage LAB, a shift from homofermentative cocci towards carnobacteria, Lactobacillus sakei/curvatus and heterofermentative rods is seen in this marinated product.
  • Hussain, Nazar; Tariq, Muhammad; Saris, Per Erik Joakim; Zaidi, Arsalan (2021)
    Introduction: Probiotic and postbiotic potential of thirty-two strains of lactic acid bacteria (LAB), obtained earlier from artisanal dairy sources in Pakistan, have been investigated against major multi-drug resistant (MDR) and food borne pathogenic bacteria. Methodology: LAB strains were identified by 16S rRNA gene sequencing and their antibacterial activity was assessed by the microdilution method. Four LAB isolates, Weissella confusa PL6, Enterococcus faecium PL7, and Lactobacillus delbrueckii PL11 and PL13 were shortlisted. Their ability to degrade lactose and safety for human consumption in terms of hemolysis and antibiotic susceptibility were assessed in vitro. The antibacterial components in the cell-free supernatants (CFSs) of isolate cultures were characterized biochemically by HPLC. Results: Acid neutralization but not protease treatment abolished the antibacterial activity of CFSs. Lactic, acetic and propionic acids were the main acids in the CFSs, and acid production peaked in the stationary phase of growth. The antibacterial activity of the LAB cultures resulted from secretion of organic acids that lowered the pH. The strains exhibited variable ability to degrade lactose and were non-hemolytic and susceptible to the most common antibiotics. Conclusions: These LAB strains are probiotic candidates for further investigation of their postbiotic role in naturally preserving processed foods and for attenuation of lactose intolerance.
  • Verni, Michela; Wang, Changyin; Montemurro, Marco; De Angelis, Maria; Katina, Kati; Rizzello, Carlo G.; Coda, Rossana (2017)
    This study investigated the metabolic traits of 27 lactic acid bacteria (LAB) strains belonging to different species, previously isolated from faba bean. The activities assayed, related to technological and nutritional improvement of fermented faba bean, included peptidases, beta-glucosidase, phytase, as well as exopolysaccharides synthesis and antimicrobial properties. In addition, the bacteria performance as starter cultures during faba bean fermentation on proteolysis, antioxidant potential, and degradation of condensed tannins were assessed. Fermentative profiling showed that only 7 out of 27 strains were able to metabolize D-raffinose, particularly Leuc. mesenteroides I01 and I57. All strains of Pediococcus pentosaceus exerted high PepN activity and exhibited beta-glucosidase activity higher than the median value of 0.015 U, while phytase activity was largely distributed among the different strains. All the weissellas, and in lower amount leuconostocs, showed ability to produce EPS from sucrose. None of the strains showed antimicrobial activity toward Staphylococcus aureus, while eight strains of P. pentosaceus exhibited a strong inhibitory activity toward Escherichia coli and Listeria monocytogenes. Generally, the doughs fermented with pediococci exhibited high amount of total free amino acids, antioxidant activity, and condensed tannins degradation. These results allowed the identification of LAB biotypes as potential starter cultures for faba bean bioprocessing, aiming at the enhancement of faba bean use in novel food applications.
  • Verni, Michela; Rizzello, Carlo Giuseppe; Coda, Rossana (2019)
    Cereals are one of the major food sources in human diet and a large quantity of by-products is generated throughout their processing chain. These by-products mostly consist of the germ and outer layers (bran), deriving from dry and wet milling of grains, brewers’ spent grain originating from brewing industry, or others originating during bread-making and starch production. Cereal industry by-products are rich in nutrients, but still they end up as feed, fuel, substrates for biorefinery, or waste. The above uses, however, only provide a partial recycle. Although cereal processing industry side streams can potentially provide essential compounds for the diet, their use in food production is limited by their challenging technological properties. For this reason, the development of innovative biotechnologies is essential to upgrade these by-products, potentially leading to the design of novel and commercially competitive functional foods. Fermentation has been proven as a very feasible option to enhance the technological, sensory, and especially nutritional and functional features of the cereal industry by-products. Through the increase of minerals, phenolics and vitamins bioavailability, proteins digestibility, and the degradation of antinutritional compounds as phytic acid, fermentation can lead to improved nutritional quality of the matrix. In some cases, more compelling benefits have been discovered, such as the synthesis of bioactive compounds acting as antimicrobial, antitumoral, antioxidant agents. When used for baked-goods manufacturing, fermented cereal by-products have enhanced their nutritional profile. The key factor of a successful use of cereal by-products in food applications is the use of a proper bioprocessing technology, including fermentation with selected starters. In the journey toward a more efficient food chain, biotechnological approaches for the valorization of agricultural side streams can be considered a very valuable help.
  • Lyhs, Ulrike; Korkeala, Hannu; Björkroth, Johanna (Elsevier, 2002)
    A total of 296 lactic acid bacteria (LAB) isolated from spoiled, vacuum-packaged ‘gravad’ rainbow trout stored at 3ºC and 8ºC were characterised and identified using a molecular approach. The isolates were initially grouped according to their HindIII restriction endonuclease profiles and further identified to species level using a rRNA gene restriction pattern (ribotype) identification database. Lactobacillus sakei, Lactobacillus curvatus and Carnobacterium piscicola were the three main species detected. Only one isolate was identified as Carnobacterium divergens. Most of the carnobacteria were found in the samples stored at 3ºC. The relative proportion of L. sakei was higher in the samples stored at 8ºC.
  • Coda, Rossana; Varis, Jutta; Verni, Michela; Rizzello, Carlo G.; Katina, Kati (2017)
    The effects of the substitution of wheat flour with faba bean flour and faba bean sourdough on the properties of composite bread were investigated. Bread was prepared by replacing wheat flour with 30% of faba bean flour, native or after sourdough fermentation. The addition of faba bean flour influenced the structure of the breads, causing a slight decrease of volume and higher hardness compared to wheat bread. However, when fermented faba bean flour was added, the crumb porosity of the bread was not affected. The addition of 30% of faba bean flour increased wheat bread protein content from 11.6 up to 16.5% of dry matter. The addition of native faba bean flour did not affect the in vitro protein digestibility, resulting similar to wheat bread (64%). On the contrary, faba bean sourdough bread showed higher protein digestibility (73%). Generally, the addition of native faba bean flour caused an improvement of the nutritional indexes of the composite bread, further enhanced when fermentation was carried out. The free amino acid profile, protein chemical score, and biological value index were the highest in faba bean sourdough bread. In addition, the predicted glycemic index was the lowest in faba bean sourdough bread. (C) 2017 Elsevier Ltd. All rights reserved.
  • Ariwo-ola, Taofiq Adewale (Helsingfors universitet, 2011)
    Polyphenolic compounds occurring naturally in knotwood of plants are known to have antimicrobial effects. The knots (i.e. the branch bases inside tree stems) and outer branches in pine trees contain a remarkably high concentration of phenolic stilbenes, while lignans are the major phenolic constituents of spruce knots. Large amount of these phenolic compounds can be extracted from wood knots at pulp and paper mills where their presence is undesirable. In Finland, marinating of broiler meat is done not only to increase or add value to the meat, but also to enhance the safety and shelf-life. These products are usually packed under a modified atmosphere for further protection against spoilage microorganisms. However, studies have revealed that addition of marinades to poultry products do not have an inhibitory effect on either some psychrotrophic anaerobic bacteria, such as Brochothrix thermosphacta or lactic acid bacteria associated with spoilage. Also, the activity of pathogenic Campylobacter jejuni is not affected by marinating. The objective of this study was to investigate the inhibitory and lethal activities of extracts from spruce (Picea spp.) and pine (Pinus spp.) knotwood and outer branches that are dissolved in ethanol against the spoilage microorganisms in modified atmosphere packaged marinated broiler products. Modified atmosphere packaged broiler products were separately inoculated with ‘normal’ marinades, marinades with 70% ethanol, marinades with a mixture of spruce and pine extracts dissolved in 70% ethanol or mixture of spruce and pine extracts in powder form. The bacterial colony forming units per gram obtained from each of the samples were analysed on de Man Rogosa and Sharpe agar at days 1, 6, 12 and 15. The results showed that there were significant differences in bacterial colony forming units per gram (P <0.05) between packages with ‘normal’ marinades and packages with extracts added to their marinades on the 12th and 15th day. It can be concluded that the addition of extracts from spruce and pine knotwood to marinades significantly retarded growth of spoilage microorganisms during the 15 day test period. However further research is warranted to characterise and establish the safety and suitability of the compound(s) in spruce and pine knotwood extracts that are responsible for inhibitory or lethal activity against the microbes that may be present in marinated poultry meat.
  • Xu, Yan; Pitkänen, Leena; Maina, Ndegwa Henry; Coda, Rossana; Katina, Kati; Tenkanen, Maija (2018)
    The aim of this study was to study the interactions between dextran and fava bean protein. Two dextrans produced by Leuconostoc pseudomesenteroides DSM 20193 and Weissella cibaria Sj 1b were purified and mixed with fava bean protein isolate (FPI) in water or in different buffers. The two isolated dextrans presented a typical dextran structure, mainly alpha-(1 -> 6) linkages (above 95%) and few alpha-(1 -> 3) branches, but they differed in molar mass and conformation. Dry-heating incubation of FPI and dextran mixture facilitated the conjugation of dextran to FPI through the Maillard reaction. Both mixed and conjugated systems were further heat-treated, and different influences of the formed covalent bonds on rheological properties were observed. The W. cibaria Sj 1b dextran had a much higher gel-strengthening ability than the Ln. pseudomesenteroides DSM 20193 dextran. The intermolecular FPI-dextran interactions played an important role in stabilizing the mixed systems at different pH.
  • Lamminen, Marjukka (Helsingfors universitet, 2014)
    The aim of this study was to investigate the esilability of white lupin (Lupinus albus) and spring wheat (Triticum aestivum) bi-crop when ensiled as a whole-crop. There were two plant mixture ratios and two growth stages in the study. Silages made with different additives were compared with untreated silages, which were as a control. The experimental silages were made at the research farm of the University of Helsinki in Viikki on August 13th and 27th, 2012. At the first growth stage (K1) wheat was at the beginning of dough stage and the pods of white lupin were green and the seeds filled 50 % of space between septa. At the second growth stage (K2) wheat was at the end of dough stage and the seeds filled 75 % of space between septa. After mowing plant species were separated and two ratios were formed. The first ratio comprised 1/3 white lupin and 2/3 wheat and the second 2/3 white lupin and 1/3 wheat of fresh weight. The additive treatments were: 1) without additive (untreated), 2) formic acid (4 l/t as a 100% acid), 3) the mixture of sodium nitrite (0,75 kg/t) and hexamine (0,5 kg/t) and 4) Lactobacillus plantarum 1x106 cfu/g. Silages were ensiled in the laboratory scale silos in triplicate. Silos were opened after 100 days of ensiling. The chemical composition of raw material at harvest and the fermentation characteristics and aerobic stability of silages were determined in the experiment. The dry matter content of plant mixtures was about 220 g/kg in the mixtures with higher proportions of lupin and about 300 g/kg in the mixtures with higher proportions of wheat. The preservation of silages were impeded by the low dry matter content and high buffering capacity of white lupin, the low sugar content of the mixtures and clostridial contamination. As the proportion of lupin increased the crude protein and sugar content of the mixture increased but the ensilability of the mixture declined. Preservation without additive produced low quality silages in all silage batches. High amounts of ammonia, butyric acid and other fermentation acids typical of bad silage fermentation were detected in the untreated silages. The fermentation quality was good in silages made with Lactobacillus plantarum at the first growth stage when the raw material was dryer and the sugar content of mixtures were higher. Based on the butyric acid and ammonia concentrations the use of Lactobacillus plantarum resulted in poor quality silages at the second growth stage. The dose of formic acid in this experiment wasn’t probably high enough in regard to the poor ensiling properties of raw material and clostridial contamination. High amounts of butyric acid were detected in all silages treated with formic acid. At the second growth stage the ammonia concentrations were also high. The most effective additive in the experiment was the mixture of sodium nitrite and hexamine resulting in good fermentation quality in all silage batches. No butyric acid was detected from the mixtures with higher proportions of wheat and amounts were extremely low also in the mixtures with higher proportions of lupin. Most of the silages were aerobically stable during 13 days of the period of measurement. Only a few silos (5 out of 48) were aerobically deteriorated and those silos were very unstable as the warming was noticed within 2 days. Most of the deteriorated silos (4) were treated with biological additive. Based on the present results the ensiling of white lupin-wheat whole-crop silage is difficult. The composition of raw material suggests that silage should be made from the mixture where the proportion of lupin is higher and cut at the earlier growth stage if the maximization of crude protein and sugar content is wanted. However, the ensilability of raw material is more difficult on the basis of dry matter content and buffering capacity. The yield is also lower than later in the growth stage. Silage additive should always be used when ensiling white lupin. The mixture of sodium nitrite and hexamine was the most effective additive in the study.
  • Nihtilä, Hanna (Helsingin yliopisto, 2019)
    Brewers’ spent grains (BSG) are by-products of the brewing industry. Utilization of BSG in food applications is challenging, due to its poor technological characteristics. Because of their water retaining properties, interactions with matrix components and impact on texture formation, bacterial exopolysaccharides (EPS) represent a promising tool for improvement of BSG properties. Among bacterial exopolysaccharides, dextran produced in situ by lactic acid bacteria (LAB) during fermentation has shown major improvements in technological and sensorial features of products prepared from various types of plant materials. The nutritious composition of BSG may support the growth of LAB and enable in situ dextran production. The aim of this study was to establish and examine the synthesis of dextran by LAB in BSG. Sixteen dextran producing LAB strains were screened for viscosity formation in BSG fermentation. The strains showing the highest viscosity formation were further assessed for fermentation performance. The more suitable fermentation temperature was traced by comparing the viscosifying performance of selected starters at 20 and 25 °C. Dextran amount was determined semi-quantitatively from selected fermented samples showing optimal results, and the presence of oligosaccharides was assessed. Sucrose, glucose, maltose and fructose amounts were analyzed to observe the relation between sugar consumption and dextran and oligosaccharides formation. Weissella confusa strains A16 and 2LABPTO5 and Leuconostoc pseudomesenteroides strain DSM20193 appeared the most promising starters for viscosity formation and thus dextran synthesis in this matrix. From the examined fermentation temperatures, strains showed the highest potential for dextran synthesis at 25 °C. The amount of synthesized dextran ranged from 1.1 to 1.7 % w/w (of the wet weight of the whole sample matrix). The rheological properties of BSG were modified via LAB fermentation and dextran synthesis, resulting in more viscous texture, and its applicability in food systems was thus potentially enhanced.
  • Laurikkala, Sini (Helsingin yliopisto, 2015)
    The literature review presents general information on fungi and mycotoxins and then deals with aflatoxins, in particular aflatoxin B1 and M1, their occurrence, significance, and current methods for controlling the risk of aflatoxin. Particular emphasis was given to studies on lactic acid bacteria (LAB) in controlling the growth of aflatoxigenic molds and binding of aflatoxins. The aim of the experimental work was to assess the ability of 171 LAB isolates originating from Kenyan naturally fermented traditional milk and maize samples (1) to inhibit the growth of Aspergillus and (2) to bind aflatoxin M1 in vitro. All the LAB isolates (n=171) were screened for their antifungal activity against A. flavus by an overlay method with 100 µl LAB culture on potato dextrose agar (PDA) plate. Out of 171 LAB isolates, mold growth was reduced by 33 isolates, of which 19 isolates were confirmed to retain their activity. These 19 LAB isolates were tested against A. flavus with three different amounts of LAB culture (50 µl, 100 µl and 200 µl). Three LAB isolates performed best against A. flavus by inhibiting the growth with all the tested amounts of LAB culture. The three LAB isolates were identified as Lactobacillus plantarum first by 16S rDNA sequence analysis and later confirmed by recA derived primers and multiplex PCR assay. The ability of 171 LAB isolates to bind AFM1 from phosphate-buffered saline (PBS) in vitro was carried out. LAB isolates were incubated with an amount equivalent to 50 ng AFM1 /ml for 4 h and then centrifuged (10 000 rpm, 10 °C) for 15 min to obtain supernatant containing unbound AFM1. The amount of unbound aflatoxin was analysed by HPLC chromatography from 51 samples. Binding ability of the analyzed isolates varied from 15,4 % to 51,5 %, and six LAB isolates were shown to bind more than 42,4 % of AFM1. The results showed that all tested indigenous LAB isolated from fermented milk and maize products manufactured in Kenya had variable ability to control the growth of A. flavus and bind AFM1 in vitro. It is suggested that such LAB strains could be used for reduction of the risk of aflatoxin contamination in food and feed chains.
  • Kianjam, Maryam (Helsingfors universitet, 2016)
    The literature review deals with faba bean and the important effects of lactic acid bacteria (LAB) fermentation on legumes. Particularly, the information about sourdough and LAB microbiota together with the main factors affecting sourdough microbial community is presented. A brief introduction regarding the methods used for LAB identification is also given. The main aim of the experimental study was to identify LAB microbiota in faba bean sourdoughs of two different varieties during backslopping procedure. Doughs from Italian (I) and Finnish (F) faba bean flours were spontaneously fermented and propagated daily through backslopping on a laboratory scale for 14 days. Samples were taken from selected propagation times (0, 1, 2, 5, 7, and 14) for microbiological and biochemical analyses. The pH values and total titratable acidity (TTA) were monitored throughout the process. Analyses of organic acids and oligosaccharides of selected samples were carried out with HPLC methods at University of Bari, Italy. The identity of the LAB isolates was revealed by sequence analysis of 16S rDNA and the differentiation of LAB strains was analyzed by randomly amplified polymorphic DNA (RAPD)-PCR. Minor changes occurred between I and F sourdoughs based on microbiological and biochemical analyses. However, several differences were found in LAB diversity between these two sourdoughs. More variety of LAB species and higher strains diversity were found in F faba bean sourdough. Besides Pediococcus pentosaceus, Leuconostoc mesenteroides, and Weissella koreensis identified in both sourdoughs, Enterococcus casseliflavus, Enterococcus faecium, Lactobacillus sakei, Lactococcus lactis, and Weissella cibaria were only detected in F sourdough. In both sourdoughs, Pediococcus pentosaceus was predominant and persistent. Also, Leuconostoc mesenteroides was found as second frequent species in both sourdoughs. According to all analyses, the maturity of sourdoughs was achieved during 5 days of propagation. This study demonstrated the importance of flour type and composition on establishing microbial ecology of sourdough. The research study encourages exploring the potential of faba bean flour in sourdough-type fermentation and encourages further investigations on the identified isolates as starter cultures for fermented faba beans and faba bean-cereal products.
  • Björkroth, Johanna; Korkeala, Hannu (International Association for Food Protection, 1997)
    Spoilage characterized by bulging as a result of gas formation in bottled ketchup was studied and resulted in growth on MRS and Rogosa selective Lactobacillus agar. Seventy randomly selected isolates were typed using restriction endonuclease analysis (ClaI, EcoRI, HindIII) and were found to have identical patterns. The strain was identified as Lactobacillus fructivorans using morphological, physiological and biochemical characteristics, combined with information obtained from rRNA gene restriction patterns. Factors affecting growth and survival of this L. fructivorans strain in production circumstances were also studied. Lactobacillus count of 105 CFU/g resulted in spoilage of inoculated ketchup samples. Spoilage occurred only in samples incubated at 15 to 30°C. L. fructivorans implicated in causing spoilage demonstrated heat resistance with a D-value of 1.2 min at 65°C. The strain did not show resistance against alkaline, active chloride containing detergent sanitizer, and also alkyldimethylbenzyl ammonium chloride and alkyldimethylethylbenzyl ammonium chloride containing sanitizer was found to be effective against it.