Starter Cultures Research Articles

SELECTION OF LACTIC ACID BACTERIA FOR RYE BREAD SOURDOUGH

Lactic acid bacteria are widely used to produce diverse type of fermented products. One of conventional applications for lactic acid bacteria is inclusion into sourdough for bread baking. These microorganisms play a key role in dough fermentation of rye flour or wheat and rye mixture since the yield of stable and well-leavened rye dough is possible only in acidic environment. Lately, despite the development of accelerated baking technologies and technological improvements, which in some cases eliminate the need for sourdough, interest in the tradition of making bread using sourdough as a source of flavoring, nutrient and health-enhancing compounds is constantly growing across the globe. It is natural therefore that focus of the researchers is centered on seeking new strains of lactic acid bacteria attractive as potential constituents of rye bread sourdough. Screening of strains-candidates to be included in the consortia for rye flour fermentation was conducted among collection cultures (23 strains), isolates from rye flour samples (154 strains) and among craft rye dough cultures for spontaneous fermentation kindly provided by private households of Minsk, Turov, Zhitkovichi (21 strains). Identification of lactic acid bacteria following examination of morphological, cultural, physiological and biochemical characteristics of the cultures and guided by the data of MALDI TOF mass spectrometry indicated that the compared microorganisms represented genera Lactiplantibacillus, Limosilactobacillus, Pediococcus, Weissella, Lactococcus. The majority of lactic acid bacteria isolated from rye flour samples belonged to genera Lactiplantibacillus and Pediococcus. Representatives of genera Lactiplantibacillus and Levilactobacillus prevailed among domestic variants of rye bread sourdoughs. Evaluation of acidogenic capacity of analyzed cultures upon 16 h fermentation in water-flour suspension by Neumann technique and organoleptic assessment of the obtained solutions sorted out for further studies 10 strains of lactic acid bacteria referred to species Levilactobacillus brevis (4 strains) Lactiplantibacillus plantarum (3 strains) and singular strains of species Lactiplantibacillus paraplantarum, Limosilactobacillus fermentum, Weissella cibaria. Glycosyl-hydrolases produced by lactic acid bacteria constituting starter cultures largely determine biochemical processes during fermentation of flour mixtures. Chromogenic substrates o-nitrophenyl-β-D-galactopyranoside, o-nitrophenyl-α-D-galactopyranoside, 4-nitrophenyl-β-D-glucopyranoside were used in 1 mmol concentration to assay activities of β-galactosidase, α-galactosidase, β-glucosidase, respectively. It was found that all tested bacteria of species Levilactobacillus brevis and Limosilactobacillus fermentum were characterized by synthesis of proteins with α-galactosidase and β-galactosidase activities in the course of growth on media with glucose and maltose. β-glucosidase activity was revealed in all representatives of species Lactiplantibacillus plantarum, Levilactobacillus brevis and Lactiplantibacillus paraplantarum. Amylolytic activity was detected in two Lactiplantibacillus plantarum strains, whereas bacteria of species Weissella cibaria displayed a weak β-glucosidase activity. An important criterion to select microbial constituents for dough fermentation is antagonistic activity toward contaminating microbiota. Antagonistic response of lactic acid bacterial cultures to causal agents of bread spoilage was demonstrated, including epidemiologically significant fungi of genera Fusarium, Aspergillus, Penicillium, etc. Analysis of obtained data has enabled to compose microbial consortia promising for further elaboration of technologies for producing active bread-making starter formulas with upgraded biotechnological properties and enhanced alimentary, nutritional and biological value.

Improving qualities of Kocho fermentation using Mandillo [Crassocephalum macropappum (Sch.Bip. ex. A.Rich.) S.Moore] as a starter culture ingredient

This study assessed the impact of adding Mandillo, an Ethiopian herbaceous plant, to the fermentation process of Kocho, a fermented food made from Enset plants. Mandillo has been traditionally used by the Shekacho people to enhance the quality and fermentation of Enset during Kocho production. Kocho samples were fermented with Mandillo stem (Kom) and without (Koki) for quality evaluation. Proximate composition, mineral content, water-holding capacity, phytic acid, tannin content, and sensory attributes were analyzed. Through comprehensive physicochemical and sensory analyses, we observed distinct improvements in Kocho quality. For Koki, the protein content increased from 5.1% to 6.0% with the use of LAB starter cultures, while Kom exhibited a 15% reduction in fermentation time (from 12 to 10 days). In terms of sensory evaluation, Koki had a 25% higher overall taste score compared to the control sample, whereas Kom demonstrated a 20% improvement in texture consistency. These findings indicate that tailored fermentation approaches can significantly enhance the nutritional and sensory qualities of both Koki and Kom. The results have important implications for improving and advancing traditional food fermentation practices in Ethiopia.

Changes to Structural and Compositional Features of Water-Soluble Arabinoxylans in Sourdough Bread.

This research investigates the influence of milling methods and starter cultures on the structural characteristics of water-extractable arabinoxylans (WE-AX) in stone-milled whole-grain flour and sourdough bread. Stone milling was conducted to generate six different whole wheat flour samples, from which sourdough bread was produced using wheat and rye starter cultures. The study found that both milling parameters and the type of starter culture significantly impacted the fine structural details of WE-AX, including sugar composition, arabinoxylan (AX) content, and the arabinose-to-xylose (A/X) ratio values. These differences were statistically significant (p < 0.05). Furthermore, transforming flour into sourdough bread resulted in the molecular degradation of AX, significantly reducing its molecular weight and leading to a more heterogeneous fine structure. This detailed characterization of AX's alterations during food processing provides insights into evaluating its potential health benefits in whole-grain products.

Unveiling the genetic basis and metabolic rewiring behind the galactose-positive phenotype in a Streptococcus thermophilus mutant

Streptococcus thermophilus (S. thermophilus) is a widely used starter culture in dairy fermentation, but most strains are galactose-negative and only metabolize glucose from lactose hydrolysis. In this study, we aimed to uncover the mechanisms underlying the acquisition of a stable galactose-positive (Gal+) phenotype in a mutant strain of S. thermophilus IMAU10636. By treating the wild-type strain with the mutagenic agent N-methyl-N-nitro-N-nitrosoguanidine, we successfully isolated a Gal+ mutant, S. thermophilus IMAU10636Y. Comparative enzyme activity assays revealed that the mutant exhibited higher β-galactosidase and galactokinase activities, but lower glucokinase and pyruvate kinase activities compared to the wild-type. High-performance liquid chromatography analysis confirmed the mutant’s enhanced ability to utilize lactose and galactose, leading to increased glucose secretion. Integrated genome and transcriptomics analyses provided deeper insights into the underlying genetic and metabolic mechanisms. We found that the metabolism regulatory network of the glycolysis / Leloir pathway was altered in the mutant, possibly due to the upregulation of the gene expression in the galR-galK intergenic region. This likely led to increased RNA polymerase binding and transcription of the gal operon, ultimately promoting the Gal+ phenotype. Additionally, we identified a mutation in the scrR gene, encoding a LacI family transcriptional repressor, which also contributed to the Gal+ phenotype. These findings offer new perspectives on the metabolic rewiring and regulatory mechanisms that enable S. thermophilus to acquire the ability to metabolize galactose. This knowledge can inform strategies for engineering and selecting Gal+ strains with desirable fermentation characteristics for dairy applications.

Enhanced biochemical, microbial, and ultrastructural attributes of reduced-fat labneh through innovative microalgae integration.

Reduced-fat labneh, while offering health benefits, often presents a challenge due to its diminished nutritional profile compared to full-fat varieties. Microalgae, such as Spirulina platensis and Chlorella vulgaris, are increasingly explored for their potential to fortify foods with essential nutrients. This study innovatively investigates the use of these microalgae to enhance the quality of reduced-fat labneh. The effect of incorporating different concentrations of both microalgae was investigated at different concentrations (0.25, 0.5, and 1%) on nutritional profile (including total solids, fat, protein, carbohydrates, essential amino acids, unsaturated fatty acids, pigments, and phenolic compounds), antioxidant activity, texture, sensory attributes, and viability of the starter culture. The findings revealed that 0.25 and 0.5% concentrations of both microalgae positively influenced the sensory characteristics of the labneh and significantly enhanced its nutritional profile. However, a 1% concentration negatively impacted sensory qualities. Chlorella vulgaris enrichment resulted in higher pH values but compromised texture attributes. Importantly, both microalgae varieties enhanced the viability of the starter culture during 21 days of refrigerated storage. The scanning electron microscope images provide visual evidence of the microstructural changes in labneh with varying concentrations of microalgae and over different storage periods. This research establishes the optimal concentrations for individual microalgae enrichment in reduced-fat labneh, offering valuable insights into their potential to improve both nutritional and sensory aspects. However, it's important to mention that while both microalgae have similar effects, they might differ in their specific impacts due to their unique nutritional profiles and physical properties. Therefore, further investigations could explore optimizing a microalgae mixture and its potential application in functional food development.

Exopolysaccharides from Weissella cibaria isolated from oats: isolation, characterisation and its application in improving the texture of set‐type yogurt

SummaryIn this study, a lactic acid bacteria strain isolated from oats was used as a producer to obtain exopolysaccharide (EPS) using MRS agar plates. The findings indicated that the bacterial strain identified as Weissella cibaria (accession number: PP515290) was shown to have good probiotic activity, adapt better to alkaline than acidic conditions, and efficiently produce EPS at concentrations of up to 7.93 g L−1. SEM images showed a smooth surface and compact particle whereas FTIR confirmed the basic functional groups of polysaccharides in the sample. Meanwhile, XRD analysis demonstrated a non‐crystalline amorphous structure and thermal analysis indicated two‐phase thermal decomposition with maximum rate at 210 °C. Subsequently, EPS from W. cibaria was applied as stabiliser in set‐type yogurt (ex situ) in comparison with yogurt using mixed culture with W. cibaria (in situ) and traditional starter culture (control). The results showed that the addition of 2% EPS significantly improved syneresis (14.31%) compared to co‐culture (27.50%) and control (29.80%) as well as increased hardness of yogurt during 2‐week refrigeration.

Application of scoby bacterial cellulose as hydrocolloids on physicochemical, textural and sensory characteristics of mango jam.

The scoby pellicle of symbiotic culture of bacteria and yeast is a by-product from kombucha fermentation. While a portion is used as starter culture, the remainder is often discarded, yet it can be a valuable source of bacterial cellulose. Scoby from black, green and oolong tea kombucha fermentation was assessed for its hydrocolloid effects in mango jam-making through evaluation of physicochemical, textural and sensory characteristics. Quality of jam was significantly improved with water activity reduction up to 22.22% to 0.679, moisture content reduction up to 37.06% to 19.92%, and a pH drop up to 5.9% to 3.19 with the use of 20 to 100 g kg-1 scoby. In colour analysis, presence of scoby led to a brighter jam due to higher values from 30.98 to a range of 31.82 to 40.83. Texture of jam with scoby gave higher gel strength and adhesiveness, with the most prominent effects from the black tea kombucha. Overall acceptability in sensory test scoring was above 70% on a nine-point hedonic scale with the 40 g kg-1 green tea kombucha scoby jam chosen as the most preferred. Scoby gave significant contributions to jam stability, appearance and texture, showing potential as a clean-label food ingredient. © 2024 Society of Chemical Industry.

Assessment of Biochemical Potential of Rhizopus oligosporus as Starter Culture to Enhance the Nutritional Value of Palm Kernel Cake for Animal Feed Formulation

The objective of this study was to assess the biochemical potential of Rhizopus oligosporus as a starter culture to enhance the nutritional value of palm kernel cake (PKC) for animal feed formulation using appropriate standard methods. Among the experimental groups, the batch of birds fed with solid-state fermented PKC as a 50% maize replacement showed a noteworthy weight gain (p &lt; 0.05) in relation to the control group, while the other experimental groups exhibited a weight loss. Serum levels of ALT, AST, ALP, creatinine, and blood urea did not show a notable difference from the reference group and those on the experimental diets. These findings collectively suggest that the pre-treatment of PKC using R. oligosporus holds the potential to elevate its nutritional quality for utilization in animal feed applications.

Alternative fermentation method of cocoa beans: The use of Lactiplantibacillus plantarum subsp.plantarum HL-15 as starter culture and valorization of cocoa pulp by-product

Inconsistency in quality remains a problem for Indonesian cocoa beans. This resulted in low-priced cocoa beans, significantly affecting the livelihood of its farmers. Optimization in cocoa bean processing methods focused on practical and high-value-added technology is urgently needed to solve the issue. This study aimed to evaluate the potential application of an alternative method based on de pulping treatment and adding Lactiplantibacillus plantarum subsp. plantarum HL-15 as a starter culture in cocoa post-harvest processing. The physical and sensorial quality of cocoa beans obtained from the method were evaluated. Microbiological growth patterns during fermentation were analyzed to better understand the effect of L. plantarum HL-15 addition. Economic comparative analysis was done to assess the feasibility of implementing the alternative method. The results showed that depulping and adding L. plantarum HL-15 before fermentation could produce high-quality cocoa beans with an outstanding sensory profile. Lactiplantibacillus plantarum subsp. plantarum HL-15 exhibited the ability to regulate microorganism consortia and suppress the growth of fungi. Combining this fermentation technique with by-product utilization based on the production of probiotic drinks could support the smallholder's livelihood by increasing the added value of cocoa beans and providing significant income.

Microbiological Evaluation of Two Mexican Artisanal Cheeses: Analysis of Foodborne Pathogenic Bacteria in Cotija Cheese and Bola de Ocosingo Cheese by qPCR.

Cotija and Bola de Ocosingo are artisanal ripened cheeses produced in Mexico. Both are made with raw bovine milk from free-grazing cows and with no starter cultures. Unlike culture-based techniques, molecular methods for pathogen detection in food allow a shorter turnaround time, higher detection specificity, and represent a lower microbiological risk for the analyst. In the present investigation, we analyzed 111 cheese samples (95 Cotija and 16 Bola de Ocosingo) by qPCR (TaqMan®) after an enrichment-culture step specific to each foodborne bacterium. The results showed that 100% of the samples were free of DNA from Listeria monocytogenes, Brucella spp., Escherichia coli enterotoxigenic (ETEC), and O157:H7; 9% amplified Salmonella spp. DNA; and 11.7%, Staphylococcus aureus DNA. However, the threshold cycle (Ct) values of the amplified targets ranged between 23 and 30, indicating DNA from non-viable microorganisms. Plate counts supported this assumption. In conclusion, 100% of the cheeses analyzed were safe to consume, and the enrichment step before DNA extraction proved essential to discern between viable and non-viable microorganisms. Hygienic milking, milk handling, cheese manufacturing, and ripening are crucial to achieve an adequate microbiological quality of cheeses made with raw milk.

A Study on The Capabilities of Cellulolytic Bacteria in Degrading Feed Fiber

The utilization of local feedstuffs is a cost-effective strategy to reduce production expenses in animal husbandry. Enhancing the nutritional quality of these feedstuffs through fermentation presents a viable approach. This study investigates the efficacy of cellulolytic bacteria in degrading fiber in three local feed materials: duckweed (Lemna minor), water hyacinth (Eichornia crassipes), and lamtoro (Leucaena leucocephala). We employed a completely randomized block design with feed types as the block and levels of starter culture as treatment. Pediococcus pentosaceus, identified for its cellulase enzyme production with a clear zone of 4 cm on starch media, was utilized as the starter culture. The experimental procedure involved spraying Pediococcus pentosaceus onto duckweed, water hyacinth, and lamtoro, followed by incubation. The results indicated that Pediococcus pentosaceus effectively produced cellulolytic enzymes and significantly reduced crude fiber in duckweed by 18.18%, in water hyacinth by 9.17%, and in lamtoro by 4.23% (p &lt; 0.05). Additionally, the crude protein content increased in all samples: by 4.69% in duckweed, 2.71% in water hyacinth, and 2.13% in lamtoro (p &lt; 0.05). Among the treatments, the optimal outcome was achieved with 3 ml of Pediococcus pentosaceus. This study demonstrates the potential of Pediococcus pentosaceus for improving the nutritional profile of local feedstuffs through fermentation.

Experimental Studies on the Siirt Herby Tulum Cheese: II. Evaluation of a New Industrial Process Model

This study was conducted to test a process that we had previously developed in parallel to the traditional Siirt Herby Cheese production method. Both raw and pasteurized Eve's milk were used parallelly in the study. Pasteurized milk was inoculated with an autochthonous starter culture which we have developed. After clot formation, breaking the clot, straining and acidification of curd by using acid whey, first pressing, adding herb and salt, and applying the second pressing stages were followed. Then, the cheese samples were packaged. No air gap was presented in the cheese containers. The entire production was completed within 24 hours. During the 120-d ripening period of the samples at 4 °C, pH was observed to be 5 and acidity was 0.7% (lactic acid). In raw milk cheese, pH was 6.8 and acidity was 1.12% at the end of the ripening period. It was determined that the method tested in this study was not recommendable for making raw milk cheese. The pasteurized milk cheese samples had at least 0.7 acidity, 5 pH, 20% fat and 20% protein; It was observed that at least 45% dry matter values could be obtained. However, the pasteurized milk cheese samples did not fully meet our expectations. The crumbling property of the cheese samples was not ideal just seen in the tradiditonal Tulum Cheeses of Türkiye. The slightly sticky and melted appearance was considered a negative property of the cheese and should be eliminated with more detailed work. Traditional production takes at least 10 d. This period may be long for industrial production. Raw milk is used in traditional production, and excessive salt is added to the cheese for hygiene purposes. Also, it is not easy to make a standard production. More research is needed to eliminate such negativities, and to recommend a valuable industrial process.

Identification of halotolerant Lysinibacillus sphaericus isolated from Indonesian traditional dry-salted fish

Abstract Halotolerant protease-producing bacteria are a potential source of culture starter for the fermentation of fishery products. To find potential culture starter that can be used for fish fermentation, isolation of indigenous halotolerant bacteria is a particularly important step. This study was carried out for the isolation and identification of proteolytic bacteria isolated from traditional dried fish in Indonesia. A total of 32 isolates were obtained from three types of dried salted fish (ikan kotok, ikan belanak, and ikan kepala batu). Out of 30 isolates, six showed casein hydrolysis on skim milk agar (SMA), however, only four isolates showed proteolytic activity on saline SMA (10% w/v NaCl) namely isolates UA10, UA11, UA12, and UA13. All strains were identified as Lysinibacillus sphaericus based on morphological and biochemical tests. Before it can be used for fermentation or other purposes, further characterization of Lysinibacillus sphaericus isolated from traditional Indonesian dried salted fish is required.

Genomic and metabolomic analysis of Latilactobacillus sakei DCF0720 for black soybean yogurt fermentation

Lactic acid bacteria are commonly used in plant-based fermentation to reduce off-flavor and improve sensory characteristics. However, there have been few studies on Latilactobacillus sakei for plant-based yogurt fermentation and, particularly, its metabolic features at the genomic level remain unclear. This study aims to analyze the fermentation characteristics of the L. sakei DCF0720 strain and compare genetics and metabolic relations. For this, DCF0720 was used to ferment the black soybean milk and conduct the physicochemical analysis and sensory test. The genomic and metabolic analyses were performed by complete genome sequencing and 500 MHz 1H NMR, respectively. As a result, DCF0720 exhibited enhanced fermentation performance and sensory evaluations at 37 °C compared to 30 °C, which is generally recognized as the optimal growth temperature for most L. sakei strains. It also produced flavor enhancing volatile compounds such as acetoin and hydroxyacetone, possessing all three key genes for acetoin biosynthesis. DCF0720 lacks 2,3-butanediol dehydrogenase, which leads to the inhibition of acetoin production. DCF0720 possesses a complete pathway to utilize primary black soybean carbon sources such as sucrose, raffinose, and stachyose. DCF0720 also possesses genes for the GH28 family, including the key enzymes in the hydrolysis of pectin substances, which means eliminating the main soybean nonstarch polysaccharides. This study demonstrates that DCF0720 is a suitable starter for plant-based yogurt fermentation, providing a better understanding of fermentation conditions with genetic and metabolic features for black soybean yogurt. Various carbon source utilization abilities with depth metabolic pathway analysis provide that DCF0720 can be employed to develop enhanced starter cultures for black soybean yogurt and diverse plant-based yogurts.

Microbial succession and flavor impact during natural fermentation of Tartary buckwheat sourdough

In this study, the succession process and driving mechanisms of microbial communities during the fermentation of Tartary buckwheat sourdough were explored using high-throughput sequencing and microbiome co-occurrence network analysis. A gas chromatograph–mass spectrometer (GC–MS) was used to monitor the dynamic evolution of flavor compounds in Tartary buckwheat sourdough at different fermentation stages. Using GC–MS and principal component analysis, 47 volatile compounds were identified as the main differential volatile compounds during fermentation. The predominant bacterial genera observed in the natural fermentation of Tartary buckwheat sourdough included Enterococcus, Weissella, Cronobacter, Lactococcus, and Pediococcus. Among fungi, Alternaria, Botrytis, Trichothecium, and Vishniacozyma were the dominant genera. The correlation analysis results revealed that Weissella, Pediococcus, Lactobacillus, Acinetobacter, and Vishniacozyma were the core functional microbes involved in flavor formation. Organic acids were the primary driving force for microbial succession. This study provides a better understanding of the relationship between microbial communities and volatile components in the natural fermentation process of Tartary buckwheat sourdough as well as useful information for improving the flavor quality of Tartary buckwheat sourdough products, thereby helping to choose starter cultures with flavor modulation ability.

The medicinal plant Buddleja asiatica and its relation to the welfare of local people in the Pan‐Himalayan region: Past, present, and future perspectives

Societal Impact StatementGlobalization and rapid shifts in culture and economy threaten indigenous and local knowledge (ILK) systems, and large intergenerational gaps in this knowledge already exist. Buddleja asiatica is a deciduous shrub or small tree with traditional medicinal applications but is currently largely overlooked as a medicinal resource. This study investigates the traditional uses of B. asiatica in indigenous communities in the Pan‐Himalayan region through ethnobotanical field surveys, with a view to preserving cultural heritage and strengthening economic resilience in these communities, as well as developing B. asiatica as a medicinal resource. Prioritizing the well‐being of mountain communities, this study aims to bridge community development with nature.SummaryBuddleja asiatica Lour. (Scrophulariaceae) is widely distributed across the Pan‐Himalayan region. It has traditional medicinal applications and cultural value, as well as ecological significance. We conducted an ethnobotanical study combining field surveys from Nepal and Xizang, China with a literature review using Web of Science (WoS) to review the ethnobotanical, phytochemical, and pharmacological aspects of this species. Our study highlights the cultural significance of B. asiatica within indigenous communities and, in particular, the use of the leaves to make a starter culture for the preparation of wine. However, an evident intergenerational gap in knowledge transfer exists. The phytochemical investigation revealed the presence of various chemical classes (carbohydrates, terpenoids, flavonoids, saponins, esters, steroids, glycosides, and fatty acids), of which 15 phytoconstituents were first reported from various parts of B. asiatica. The potential medicinal properties of these chemicals include anti‐inflammatory, antioxidant, cytotoxic, antihepatotoxic, antimicrobial, and cholinesterase activities. We combine these lines of evidence to show the prospects for the livelihoods of local people across this region and propose future research directions.

Lactic and propionic acid bacteria starter cultures for improved nutritional properties of pea, faba bean and lentil

Increasing plant-based food consumption as a sustainable and health-oriented alternative to meat is pivotal. Pulses are rich in proteins, minerals, and vitamins; however, they also contain antinutritional compounds, impairing their nutritional value. This study addresses this challenge through the development and application of four distinct microbial consortia in pulse-based fermentations, featuring lactic acid bacteria or a combination of lactic and propionic acid bacteria. Microbial starters significantly reduced galacto-oligosaccharides in all pulse materials, concurrently degrading vicine and convicine in faba beans, while the impact on tannins in faba beans and lentil was moderate. Fermentation with lactic acid and propionic acid bacteria consortia exhibited notable vitamin B12 production, and the effect on the content of phenolic compounds of the studied pulses was also evidenced. Additionally, genomic analyses discerned distinctive profiles among the samples, elucidating the microbial community dynamics shaping fermentation outcomes. The results of this study proved how fermentation can advance the development of pulse-based products with improved nutritional and sustainability attributes.

Genomic and phenotypic analysis unveiling the carbohydrate metabolic characteristics of Leuconostoc citreum SH12 in plant-based fermentation

Leuconostoc citreum has been widely utilized for industrial fermentation. Previously, we found Leuc. citreum SH12 as a starter culture, exhibited superior fermentation characteristics in plant-based food, but its genomic, evolutionary and carbohydrate metabolic features remained unclear. This study aimed to reveal the metabolic characteristics of Leuc. citreum SH12 in response to various carbon sources by genomic and phenotypic analysis. By multiple sequencing technology, we assembled the 1.84 Mb complete genome of Leuc. citreum SH12 and identified 193 carbohydrate metabolism genes involved in the KEGG annotation, including 59 carbohydrate-active enzymes (CAZymes) genes. Comparative genome analysis indicated that Leuc. citreum SH12 had carbohydrate metabolism pathways similar to other Leuc. citreum, but it had 27 specific genes annotated as ABC transporters and hypothetical proteins, probably representing great resilience to the environment. The reconstruction of carbohydrate metabolic pathways and carbon utilization tests showed that Leuc. citreum SH12 could metabolize glucose, sucrose, fructose and maltose well, followed by xylose, arabinose, mannose and cellobiose, but could not utilize galactose, lactose, raffinose and stachyose. Soymilk fermentation test indicated that the strain could produce mannitol, and water-soluble and water-insoluble α-glucans. This study provided insights into a deeper understanding of the genomic and carbohydrate metabolic characteristics of Leuc. citreum SH12, and implied its potential application in plant-based fermented food.

Impact of microbial milk quality on mesophilic starter culture metabolism: A metaproteomics approach

Using a metaproteomics approach, we showed that the initial milk quality impacts the proteome allocation of starter cultures used in cheese production and can be considered a fundamental source of cheese quality batch-to-batch variation. Raw milk was spiked with a highly proteolytic strain of Pseudomonas trivialis, previously isolated from raw milk, and incubated for 1, 3, and 6 days at refrigerated temperature. After incubation, the milk was heat-treated and then fermented with a mesophilic starter culture commonly used to produce Gouda-type cheeses. The development of metabolites was analyzed and a taxonomical and functional characterization of the starter culture was performed. Milk storage time impacted both the metaproteome of the starter culture, consequently affecting metabolite levels after fermentation and the level of protein expressed by the different taxa; Lactococcus protein was more abundant in samples made from milk stored longer with Pseudomonas while proteins expressed by Leuconostoc spp. decreased in abundance.

Microbial diversity, aflatoxin M1 contamination and potential lactic acid starters for commercially produced traditional fermented dairy beverages, a case of Bongo from Uganda

This was a cross sectional study that examined the microbial ecology and aflatoxin M1 contamination in commercially produced Bongo, a traditionally fermented dairy beverage from Uganda. It also involved isolation and preliminary evaluation of defined starter cultures for Bongo. Microbial analyses were done by agar plating. Microbial identification was initially done by biochemical testing and microscopy. Followed by 16S rRNA and Internal Transcribed Spacer (ITS) region sequencing for bacteria and yeasts, respectively. Community DNA was studied using Next Generation Sequencing (NGS). Aflatoxin M1 was determined using Ultra High Pressure Liquid Chromatography - Triple Quadrupole Mass Spectrometry. (GTG)5 Rep PCR fingerprinting was used to cluster candidates for starter culture evaluation. The rates of acidification of cow milk by candidate LAB coupled with sensory acceptability of the milk they fermented were the criteria for the selection of the starter cultures. Results indicated that lactic acid bacteria (LAB) and yeasts were the dominant groups. Molds, coliforms, enterococci and staphylococci were also detected. Aflatoxin M1 were insignificant. Based on agar plating technique, lactococci and lactobacilli were dominant, however, NGS showed Streptococci. Agar plating also showed Saccharomyces as dominant, but NGS showed Dipodascus. Cluster analysis identified 18 LAB, which were evaluated for starter culture properties. Three showed promise suggesting that they could be used for commercial production of cultured milks like Bongo.