Brewers' spent grain (BSG) is a major side-stream from the beer industry, with an annual estimated production of 39 million tons worldwide. Due to its high nutritional value, high abundance and low ...price, it has been proposed as an ingredient in human food. Here we investigated the ability of different lactic acid bacteria to produce the flavor molecule acetoin in liquid BSG extract, in order to broaden the possibilities of utilization of BSG in human food.
All the investigated lactic acid bacteria (LAB) covering the Leuconostoc, Lactobacillus and Lactoccocus species were able to convert the fermentable sugars in liquid BSG into acetoin. Production levels varied significantly between the different LAB species, with Leuconostoc pseudomesenteroides species reaching the highest titers of acetoin with only acetate as the main byproduct, while also being the fastest consumer of the fermentable sugars present in liquid BSG. Surprisingly, the currently best investigated LAB for acetoin production, L. lactis, was unable to consume the maltose fraction of liquid BSG and was therefore deemed unfit for full conversion of the sugars in BSG into acetoin. The production of acetoin in Leu. pseudomesenteroides was pH dependent as previously observed in other LAB, and the conversion of BSG into acetoin was scalable from shake flasks to 1 L bioreactors.
While all investigated LAB species produced acetoin under aerobic conditions, Leu. pseudomesenteroides was found to be an efficient and scalable organism for bioconversion of liquid BSG into a safe acetoin rich food additive.
•Brewers' spent grain can be used as a substrate for acetoin production in lactic acid bacteria•Of the strains tested, Leuconostoc pseudomesenteroides strains was able to reach the highest titers of acetoin.•The production rate of acetoin was scalable from shake flask to 1 L fermenters.•Some Leuconostoc pseudomesenteroides strains showed net lactate consumption in brewers' spent grain.
In order to improve the flavor profiles, food security, probiotic effects and shorten the fermentation period of traditional fermented foods, lactic acid bacteria (LAB) were often considered as the ...ideal candidate to participate in the fermentation process. In general, LAB strains possessed the ability to develop flavor compounds via carbohydrate metabolism, protein hydrolysis and amino acid metabolism, lipid hydrolysis and fatty acid metabolism. Based on the functional properties to inhibit spoilage microbes, foodborne pathogens and fungi, those species could improve the safety properties and prolong the shelf life of fermented products. Meanwhile, influence of LAB on texture and functionality of fermented food were also involved in this review. As for the adverse effect carried by environmental challenges during fermentation process, engineering strategies based on exogenous addition, cross protection, and metabolic engineering to improve the robustness and of LAB were also discussed in this review. Besides, this review also summarized the potential strategies including microbial co-culture and metabolic engineering for improvement of fermentation performance in LAB strains. The authors hope this review could contribute to provide an understanding and insight into improving the industrial functionalities of LAB.
•Functional roles of LAB during food fermentation were reviewed.•Application of systems biology and microbial physiology in LAB was discussed.•Engineering strategies to improve industrial functionalities of LAB were summarized.
In this study, the effects of single probiotics Lacticaseibacillus casei CGMCC1.5956 (L. casei 56) and Levilactobacillus brevis CGMCC1.5954 (L. brevis 54) and their combination on the quality of ...yogurt as fermented milk were investigated. The main finding was that binary probiotics might promote L. brevis 54 to produce l-glutamic acid and pyruvic acid thereby enhancing probiotic growth and antioxidant capacity. Glycine, serine and threonine metabolism and biosynthesis of amino acids might be considered the main reasons for the binary probiotics promoted the growth of L. brevis 54. A total of 65 volatile flavor substances were identified, including carbonyl compounds, alcohols, aldehydes, and acids. Differences in the metabolic profiles and pathways of volatile and nonvolatile flavor substances between single and binary probiotic bacteria were identified by metabolomics. A mapping of the action of single and binary probiotic flora was provided, which could guide the development of yogurt with unique flavor, high probiotic content, and strong antioxidant capacity.
Effect of single probiotic L. casei 56 and L. brevis 54 and their combination on yogurt quality. A simplified version of the experimental protocol conducted in this study. Display omitted
•The effects of single and binary probiotics on yogurt quality were compared.•Binary probiotics enhanced the antioxidant capacity of yogurt.•The Glycine, serine and threonine metabolism could enhance the growth of L. brevis 54.•Binary probiotics promoted the production of l-Glutamic acid and Pyruvic acid.
Sourdough is used in production of (steamed) bread as leavening agent (type I sourdoughs) or as baking improver to enhance flavour, texture, and shelf life of bread (type II sourdoughs). The ...long-term propagation of sourdoughs eliminates dispersal limitation and consistently leads to sourdough microbiota that are composed of host adapted lactobacilli. In contrast, community assembly in spontaneous cereal fermentations is limited by dispersal and nomadic or environmental lactic acid bacteria are the first colonizers of these sourdoughs.
Propagation of sourdoughs for use as sole leavening agent (type I sourdoughs) dictates fermentation conditions that select for rapid growth. Type I wheat- and rye sourdoughs are consistently populated by insect-adapted lactobacilli, particularly Lactobacillus sanfranciscensis, which is characterized by a small genome size and a restricted metabolic potential. The diverse fermentation conditions employed in industrial or artisanal Type II sourdough fermentation processes also result in a more diverse microbiota. Nevertheless, type II sourdoughs are typically populated by vertebrate host adapted lactobacilli of the L. delbrueckii and L. reuteri groups. Metabolic traits of host-adapted lactobacilli that enhance competitiveness in intestinal ecosystems also provide technological functionality in bread making. Examples include formation of exopolysaccharides, arginine-, glutamine- and glutamate based mechanisms of acid resistance, and glycosyl hydrolases that reduce FODMAP levels in sourdough and sourdough bread. In conclusion, consideration of the lifestyle of sourdough lactobacilli facilitates the selection of competitive and functional sourdough starter cultures.
The food industry generates a vast amount of food waste. Nevertheless, several types of food waste, i.e. those deriving from fruits, vegetables, grains, and other plant-based food production and ...processing chains, still contain valuable nutritional and bioactive compounds thus having the potential to be converted into value-added products. Several approaches have been investigated as pre-treatment of food waste to improve the nutritional, functional, and technological properties before to re-inclusion in food production. Sourdough fermentation, either spontaneous or through selected microbial strains, appears to be a suitable and sustainable tool for upcycling plant-derived food waste.
This review reveals the latest insights into the potential of sourdough fermentation to recycle milling by-products, brewers' spent grain, wasted bread, and miscellaneous plant wastes.
Sourdough biotechnology is suitable for improving the sustainability of several food chains. Nevertheless, due to the significant effect of the presence, growth, and metabolic activity of specific microorganisms on the quality of the final products, an accurate set-up and optimization of tailored fermentation processes is highly suggested.
•Sourdough fermentation is a tool to improve nutritional value of food waste.•Microbial starter selection is of main importance for tailored fermentations.•Sourdough fermentation improves the sustainability of several food chains.
Lactic Acid Bacteria (LAB) have long been recognized as having a significant impact ranging from commercial to health domains. A vast amount of research has been carried out on these microbes, ...deciphering many of the pathways and components responsible for these desirable effects. However, a large proportion of this functional information has been derived from a reductionist approach working with pure culture strains. This provides limited insight into understanding the impact of LAB within intricate systems such as the gut microbiome or multi strain starter cultures. Whole genome sequencing of strains and shotgun metagenomics of entire systems are powerful techniques that are currently widely used to decipher function in microbes, but they also have their limitations. An available genome or metagenome can provide an image of what a strain or microbiome, respectively, is potentially capable of and the functions that they may carry out. A top-down, multi-omics approach has the power to resolve the functional potential of an ecosystem into an image of what is being expressed, translated and produced. With this image, it is possible to see the real functions that members of a system are performing and allow more accurate and impactful predictions of the effects of these microorganisms. This review will discuss how technological advances have the potential to increase the yield of information from genomics, transcriptomics, proteomics and metabolomics. The potential for integrated omics to resolve the role of LAB in complex systems will also be assessed. Finally, the current software approaches for managing these omics data sets will be discussed.
•Thirteen LAB strains with high antifungal activity were selected from 224 strains.•The two Lactobacillus plantarum strains could control the green mold of citrus.•The main antifungal substances ...produced by Lactobacillus plantarum were analyzed.•Bacteriocin encoding genes of Lactobacillus plantarum were predicted.
This study screened lactic acid bacteria (LAB) in pickle and cured meat, explored their potential biocontrol ability against Penicillium digitatum on citrus fruit, and evaluated the inhibitory substances produced by promising biocontrol agents. A total of 224 strains were isolated. Thirteen isolates demonstrated clear inhibition zones to P. digitatum and they were identified to be Lactobacillus plantarum, Lactobacillus parafarraginis, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus buchneri, and Weissella paramesenteroides. Washed cell suspension and cell-free supernatant (CFS) of 13 isolates inhibited the growth of P. digitatum in vitro. L. plantarum CKXP13 and L. plantarum CWXP24 showed biocontrol activity in vivo. Antifungal activity of CFS of L. plantarum CKXP13 and L. plantarum CWXP24 was significantly reduced after pH-neutralization, catalase, protease treatment. It suggested that the antimicrobial substances produced by L. plantarum CKXP13 and L. plantarum CWXP24 included organic acid, hydrogen peroxide and proteinaceous compound. Mining of genome data from L. plantarum CKXP13 and L. plantarum CWXP24 showed the presence of bacteriocin encoding genes that 5 bacteriocin encoding genes were identified in L. plantarum CKXP13 and 1 bacteriocin encoding genes in L. plantarum CWXP24. These results suggested that L. plantarum CKXP13 and L. plantarum CWXP24 have potential as biocontrol agents of citrus green mold.
Gamma aminobutyric acid (GABA) is a non-protein amino acid that is widely distributed in nature and its physiological importance goes beyond its role as an inhibitory neurotransmitter of the central ...nervous system in mammals. Since microbial fermentation is one of the most promising methods to obtain GABA, the production of this metabolite by several strains of lactic acid bacteria isolated from quinoa and amaranth sourdoughs was investigated. Lactobacillus brevis CRL 2013 produced the highest GABA levels, reaching 265 mM when optimal culture conditions were set up. The fermentative profile showed that CRL 2013 was able to catabolize carbohydrates through the phosphoketolase pathway yielding variable amounts of lactic acid, acetate and ethanol, which depended on the type of carbon source available and the presence of external electron acceptors such as fructose. Enhanced growth parameters and low GABA synthesis were associated to pentose fermentation. This impairment on GABA production machinery was partially overpassed by the addition of ethanol to the culture media. These results support the potential use of L. brevis CRL 2013 as a starter culture for the manufacture of GABA-enriched functional foods and provide further insights to the understanding of the GAD system regulation in lactic acid bacteria.
•L. brevis CRL 2013, isolated from quinoa sourdough, produced high levels of GABA.•Final GABA production is among the highest for lactobacilli grown in batch culture.•Enhanced growth rates and low GABA synthesis were associated to pentose fermentation.•The impairment on GABA production was partially restored by the addition of ethanol.
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