Amino acid profile affecting the lactic acid bacterial community in kimoto seed mash at various brewing years.

The transferability of antimicrobial resistance from lactic acid bacteria (LAB) to potential pathogenic strains was studied using in vitro methods and mating in a food matrix. Five LAB donors containing either erythromycin or tetracycline resistance markers on transferable elements were conjugally mated with LAB (Enterococcus faecalis, Lactococcus lactis) and pathogenic strains (Listeria spp., Salmonella ssp., Staphylococcus aureus, and Escherichia coli). In vitro transfer experiments were carried out with the donors and recipients using both the filter and plate mating methods. The food matrix consisted of fermented whole milk (fermented with the LAB donors) with the pathogenic recipients added as contaminants during the production process. All transconjugants were confirmed by phenotypic and molecular methods. Erythromycin resistance transfer from LAB strains to Listeria spp. was observed using both in vitro mating methods at high transfer frequencies of up to 5.1 x 10(-4) transconjugants per recipient. Also, high frequency transfer (ranging from 2.7 x 10(-8) up to 1.1 x 10(-3) transconjugants per recipient) of both erythromycin and tetracycline-resistance was observed between LAB species using in vitro methods. No resistance transfer was observed to Salmonella spp., Staphylococcus aureus, and E. coli. The only conjugal transfer observed in the fermented milk matrix was for tetracycline resistance between two LAB strains (at a transfer frequency of 2.6 x 10(-7) transconjugants per recipients). This study demonstrates the transfer of antimicrobial resistance from LAB to Listeria spp. using in vitro methods and also the transfer of resistance between LAB species in a food matrix. It highlights the involvement of LAB as a potential source of resistance determinants that may be disseminated between LAB and pathogenic strains including Listeria spp. Furthermore, it indicates that food matrices such as fermented milks may provide a suitable environment to support gene exchange.

Identification of lactic acid bacteria in the rumen and feces of dairy cows fed total mixed ration silage to assess the survival of silage bacteria in the gut

Diversity of lactic acid bacteria in suan-tsai and fu-tsai, traditional fermented mustard products of Taiwan

Twenty two strains of lactic acid bacteria (LAB) were isolated from 30 samples of commercial Nigerian bottled yoghurt (produced on a small scale). Isolates were phenotypically characterized and their technological properties such as acidification, exopolysaccharides (EPS) production, enzymatic activities, biogenic amine production and bacteriocin production were studied following standard procedures. The population of LAB in the yoghurt samples varied between 0.00 and 6.63 log cfu ml-1. The pH and titratable acidity ranged from 3.80 to 4.48 and 0.73 to 1.78% lactic acid respectively. The isolated LAB strains belonged to Lactobacillus, Lactococcus, Leuconostoc, Streptococcus and Enterococcus genera. Thirteen strains showed proteolytic activity while four strains showed high lipolytic activity. The LAB strains exhibited medium to low acidification activities. About 77% of the LAB strains produced EPS. Six strains produced biogenic amines. Seven strains showed antagonistic properties due to organic acid against indicator organisms (Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli and Proteus vulgaris) while two strains (Enterococcus faecalis and Lactococcus cremoris) produced additional inhibitory substances againstK. pneumoniae. The results revealed that the assayed commercial Nigerian bottled yoghurts contain several LAB species and genera different from Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. The production of biogenic amine by some of the LAB strains is undesirable in yoghurt. The technological properties of the LAB associated with the fermented milk produced on a small scale will help in the selection and development of beneficial strains as starter or adjunct cultures. Key words: Yoghurt, lactic acid bacteria, technological properties, strain selection.

Fermented meat products are defined as meat that is inoculated with a microbial starter culture during processing under controlled condition, or meat allowed to ferment by natural fermentation meat microbial flora to give desirable characteristics. Fermentation of meat is mainly by lactic acid bacteria (LAB). Their biochemical characteristics project them as sugar fermentative, catalase and nitration reduction negative bacteria. This report is based on a preliminary research of isolation and characterization of microbes in fermented meat products on selected Ghanaian markets. The work specifically seeks to isolate and identify both essential and pathogenic microbes in fermented meat. Identification of microbial species is important for consumer protection and food law enforcement. In this study, samples of fermented bush meats and fermented sausages from selected Ghanaian markets were analyzed for their microbial content and load. Isolated microbes in samples were identified as Lactic acid Bacteria species, Streptococci species, Staphylococci species and Micrococcus species. Lactic acid Bacteria species (LAB) and micrococci species are characterized as essentially non pathogenic bacteria species whiles streptococci species and staphylococci species are characterized as the pathogen species. Isolates obtained from fermented bush meat were identified as LAB, staphylococci and streptococci species whiles isolates of fermented sausage were also identified as LAB and micrococci species. The total variable count for fermented sausage on an average was 1.3× 105 cfu, for smoked fermented bush meat the average loads was 2× 105 cfu whiles for fresh fermented bush meat the load was 2.5× 106 cfu. Key words: Meat, bush meat, fermented meat products, food microbiology, food safety, Kumasi, Ghana.

Sourdough is typically characterized by the complex microbial communities mainly comprising of yeasts and lactic acid bacteria (LAB). The objective of this study was to explore the microbiota of Chinese traditional sourdoughs collected from different areas of China using culture-dependent and denaturing gradient gel electrophoresis (DGGE) methods. A total of 131 yeasts, 2 molds, and 106 LAB strains were isolated and identified. Based on the culture-dependent analysis, the populations of yeasts and LAB were at the level of 10(5) to 10(7) and 10(6) to 10(7) cfu/g, respectively. Similarly, the results of RT-qPCR showed that the values of total yeasts and LAB populations were in the range of 10(6) to 10(7) and 10(7) to 10(8) copies/g, respectively. Using culture-dependent method, a total of 7 yeasts, 2 molds and 7 LAB species were identified. Results showed that Saccharomyces cerevisiae and Lactobacillus plantarum were the predominant species among the yeasts and LAB microflora. Similarly, using PCR-DGGE approach, 7 yeasts, 1 mold and 9 LAB species were detected. The yeast, S. cerevisiae, represented the predominant, while the yeast Candida tropicalis represented the subdominant species of the yeast community. Among the LAB community, Lactobacillus sanfranciscensis was the predominant species, while Lactococcus qarvieae, Enterococcus faecium, Lactobacillus delbrueckii and Enterococcus cecorum were among the less dominant species. In this study, microbiota of Chinese sourdoughs was investigated using culture-dependent and PCR-DGGE methods. It will provide deeper insights into the complex microbial ecosystems of sourdough. On the other hand, it will provide opportunity to utilize the potential of selected strains yeasts and LAB to obtain more desirable fermented food.

This study identified the lactic acid bacteria (LAB) biota and the volatilome profile of 28 typical sourdoughs of Irpinia—a large area of the Campania region of Southern Italy where numerous breads are produced, even today, following the ancient procedures of sourdough fermentation and for which information on the microbiological and sensory profile is lacking in literature. For this purpose, microbial quality, LAB biodiversity, chemical, and technological characteristics, as well as aroma profile by solid-phase microextraction technique (SPME)–gas chromatography/mass spectrometry (GC/MS) of Irpinian sourdoughs were investigated. The dominant LAB microbiota was examined by both culture-dependent and culture-independent methods Polymerase Chain Reaction/Denaturing Gradient Gel Electrophoresis (PCR-DGGE). Results showed a high biodiversity in LAB community whereas the most frequent lactobacilli species recognized were Lactobacillus plantarum (ca. 22% of total LAB isolates), Lactobacillus sanfranciscensis (11%), Lactobacillus paralimentarius (8%), and Lactobacillus rossiae (6.5%), whereas LAB cocci could be mainly referred to Pediococcus pentosaceus (9.5% of total LAB isolates), Leuconostoc spp. (7.8%), and Weissella cibaria (7.7%). Sourdoughs were characterized by the dominance of one or two LAB species, thus proving that the environment influences the selection and the establishment of few key LAB species and that no specific correlation can be traced between microbial composition and geographical origin of the samples. Furthermore, although sourdoughs were characterized by different qualitative and quantitative volatile organic compound (VOC) compositions, no noticeable correlation between volatilome profile and geographical origin was found. However, it emerged that for more isolated locations, it was possible to find the existence of microbial biotypes and sensory profiles with a strong identity, thus revealing the existence of highly traditional and evocative bread recipes in those geographical contexts.

Evaluation of lactic acid bacteria and yeast diversity in traditional white pickled and fresh soft cheeses from the mountain regions of Serbia and lowland regions of Croatia

Diversity and probiotic potentials of lactic acid bacteria isolated from gilaburu, a traditional Turkish fermented European cranberrybush (Viburnum opulus L.) fruit drink

“Nostrano-cheeses” are traditional alpine cheeses made from raw cow's milk in Trentino-Alto Adige, Italy. This study identified lactic acid bacteria (LAB) developing during maturation of “Nostrano-cheeses” and evaluated their potential to produce γ-aminobutyric acid (GABA), an immunologically active compound and neurotransmitter. Cheese samples were collected on six cheese-making days, in three dairy factories located in different areas of Trentino and at different stages of cheese ripening (24 h, 15 days, and 1, 2, 3, 6, and 8 months). A total of 1,059 LAB isolates were screened using Random Amplified Polymorphic DNA-PCR (RAPD-PCR) and differentiated into 583 clusters. LAB strains from dominant clusters (n = 97) were genetically identified to species level by partial 16S rRNA gene sequencing. LAB species most frequently isolated were Lactobacillus paracasei, Streptococcus thermophilus, and Leuconostoc mesenteroides. The 97 dominant clusters were also characterized for their ability in producing GABA by high-performance liquid chromatography (HPLC). About 71% of the dominant bacteria clusters evolving during cheeses ripening were able to produce GABA. Most GABA producers were Lactobacillus paracasei but other GABA producing species included Lactococcus lactis, Lactobacillus plantarum, Lactobacillus rhamnosus, Pediococcus pentosaceus, and Streptococcus thermophilus. No Enterococcus faecalis or Sc. macedonicus isolates produced GABA. The isolate producing the highest amount of GABA (80.0±2.7 mg/kg) was a Sc. thermophilus.

Dense tracking of the dynamics of the microbial community and chemicals constituents in spontaneous wheat sourdough during two months of backslopping

Evaluation of lactic acid bacterial communities in spontaneously-fermented dairy products from Tajikistan, Kyrgyzstan and Uzbekistan using culture-dependent and culture-independent methods

Occurrence of biogenic amine-forming lactic acid bacteria in wine and cider

ABSTRACTThe spontaneous microbiota of wheat sourdough, often comprising one yeast species and several lactic acid bacteria (LAB) species, evolves over repeated fermentation cycles, which bakers call backslopping. The final product quality largely depends on the microbiota functions, but these fluctuate sometimes during the initial months of fermentation cycles due to microbiota evolution in which three phases of LAB relay occur. In this study, the understanding of yeast-LAB interactions in the start of the evolution of the microbiota was deepened by exploring the timing and trigger interactions when sourdough yeast entered a preestablished LAB-relaying community. Monitoring of 32 cycles of evolution of 6 batches of spontaneous microbiota in wheat sourdoughs revealed that sourdough yeasts affected the LAB community when the 2nd- or 3rd-relaying types of LAB genera emerged. In in vitro pairwise cocultures, all 12 LAB strains containing the 3 LAB-relaying types arrested the growth of a Saccharomyces cerevisiae strain, a frequently found species in sourdoughs, to various extents by sugar-related interactions. These findings suggest competition due to different affinities of each LAB and a S. cerevisiae strain for each sugar. In particular, maltose was the driver of S. cerevisiae growth in all pairwise cocultures. The functional prediction of sugar metabolism in sourdough LAB communities showed a positive correlation between maltose degradation and the yeast population. Our results suggest that maltose-related interactions are key factors that enable yeasts to enter and then settle in the LAB-relaying community during the initial part of evolution of spontaneous sourdough microbiota.IMPORTANCE Unpredictable evolution of spontaneous sourdough microbiota sometimes prevents bakers from making special-quality products because the unstable microbiota causes the product quality to fluctuate. Elucidation of the evolutionary mechanisms of the sourdough community, comprising yeast and lactic acid bacteria (LAB), is fundamental to control fermentation performance. This study investigated the mechanisms by which sourdough yeasts entered and settled in a bacterial community in which a three-phase relay of LAB occurred. Our results showed that all three layers of LAB restricted the cohabiting yeast population by competing for the sugar sources, particularly maltose. During the initial evolution of spontaneous sourdough microbiota, yeasts tended to grow synchronously with the progression of the lactic acid bacterial relay, which was predictably associated with changes in the maltose degradation functions in the bacterial community. Further study of ≥3 species’ interactions while considering yeast diversity can uncover additional interaction mechanisms driving the initial evolution of sourdough microbiota.

Winter wheat is a suitable crop to be ensiled for animal feed and China has the largest planting area of this crop in the world. During the ensiling process, lactic acid bacteria (LAB) play the most important role in the fermentation. We investigated the natural population of LAB in whole-crop wheat (WCW) and examined the quality of whole-crop wheat silage (WCWS) with and without LAB inoculants. Two Lactobacillus plantarum subsp. plantarum strains, Zhengzhou University 1 (ZZU 1) selected from corn and forage and grass 1 (FG 1) from a commercial inoculant, were used as additives. The silages inoculated with LAB strains (ZZU 1 and FG 1) were better preserved than the control, with lower pH values (3.5 and 3.6, respectively) (p<0.05) and higher contents of lactic acid (37.5 and 34.0 g/kg of fresh matter (FM), respectively) (p<0.05) than the control. Sixty LAB strains were isolated from fresh material and WCWS without any LAB inoculation. These LAB strains were divided into the following four genera and six species based on their phenotypic, biochemical and phylogenetic characteristics: Leuconostoc pseudomesenteroides, Leuconostoc citreum, Weissella cibaria, Lactococcus lactis subsp. lactis, Lactobacillus buchneri, and Lactobacillus plantarum subsp. plantarum. However, the prevalent LAB, which was predominantly heterofermentative (66.7%), consisted of Leuconostoc pseudomesenteroides, Leuconostoc citreum, Weissella cibaria, and Lactobacillus buchneri. This study revealed that most of isolated LAB strains from control WCWS were heterofermentative and could not grow well at low pH condition; the selective inoculants of Lactobacillus strains, especially ZZU 1, could improve WCWS quality significantly.