Diacetyl Production Research Articles

Lactic acid bacteria from fermented products: Antimicrobial activity and metabolite production

In the present study, lactic acid bacteria (LAB) isolated from various fermented food sources, were studied on their antimicrobial properties alongside quantifying the production levels of lactic acid and diacetyl. Based on the findings of 16S rRNA sequencing, Pediococcus spp. were identified in 4 out of 11 isolates, Lactiplantibacillus spp. in 2 isolates, Leuconostoc spp. in 2 isolates, and Enterococcus spp. in 3 isolates. Except for isolate 8, all tested isolates demonstrated inhibitory effects against the pathogens used in the antimicrobial activity assays conducted in this study. Isolate F2 exhibited the highest lactic acid production, reaching a concentration of 10.07 mg/mL, while isolate 8 showed the highest diacetyl production at 0.8 µg/mL. Particularly, strains 40, 50, F2, AF1, and AF2 exhibited significant lactic acid production and demonstrated strong antimicrobial effects. Consequently, isolates exhibiting elevated levels of lactic acid production also demonstrated heightened antimicrobial effects, suggesting a contributory role of lactic acid production in antimicrobial activity.

A Novel Bioprotective Strain of Lactiplantibacillus plantarumF2-Physiological, Genetical, and Antimicrobial Characterization.

Lactiplantibacillus plantarum is a member of lactic acid bacteria that improves the quality of fermented foods while also having a positive impact on human health. In this study, L. plantarum F2 was studied for characteristics such as biochemical and genetic identification, metabolite production, antimicrobial activity, and plasmid content. This strain exerts antimicrobial activity against some Gram-positive and Gram-negative pathogens (Listeria monocytogenes, Staphylococcus aureus, Salmonella, and Escherichia coli) with inhibition zone diameters ranging between 17.0 and 29.0 mm; it can ferment glucose, arabinose, galactose, lactose, and demonstrated the ability to grow at high temperature (50°C). Another physiological specification of the strain was the morphology of the isolate in selective medium, the de Man, Rogosa, Sharpe medium (MRS medium containing triphenyl tetrazolium chloride), which exhibits a chromogenic colony (characterized as purple colonies) on the modified-MRS (mMRS) medium. Metabolites such as lactic acid and diacetyl production of the strain F2 were also investigated using chromatography and found to be 10.07 and 0.05 µg/mL, respectively. The peptides of the isolate's cell-free supernatant were determined to be ∼80 kDa, and finally, the plasmid isolated from the strain F2 was identified as L. plantarum strain KLDS1.0386 plasmid p4, which may be responsible for some characteristic properties, such as antimicrobial peptide production of the strain.

Unveiling the Potential of Lactic Acid Bacteria from Serbian Goat Cheese.

This study aimed to unleash the potential of indigenous lactic acid bacteria (LAB) originating from traditionally made Serbian goat cheese. Following the isolation and identification of the LAB, the safety aspects of the isolates were evaluated through tests for hemolytic activity and antibiotic sensitivity. The selected isolates were then tested for various technological properties, including growth in methylene blue, proteolytic activity, acidification, curd formation ability in both pure and enriched goat milk, diacetyl production, antagonistic potential against other LAB, and biofilm formation ability. The results indicated that Lactococcus spp., Lacticaseibacillus spp., and Lactiplantibacillus spp. did not exhibit α or β hemolysis, while enterococci displayed α hemolysis. A higher number of isolates demonstrated sensitivity to ampicillin, tetracycline, and streptomycin, while sensitivity to gentamicin and vancomycin was strain-dependent. Based on the evaluation of technological properties, Lacticaseibacillus paracasei M-1 and Lactiplantibacillus plantarum C7-7, C7-8, and C14-5 showed promising characteristics. Additionally, Lactococcus lactis subsp. lactis strains C0-14 and C21-8 emerged as promising candidates with notable technological properties. Notably, certain indigenous strains LAB exhibit promising technological properties and safety profiles. These characteristics make them suitable candidates for use as starter or adjunct cultures in goat's milk cheese production, potentially enhancing the quality and safety of the cheese as well as hygiene practices among small-scale dairy producers.

Screening and characterization of Enterococcus durans isolates from raw organic milk in Southern Brazil: Assessing technological potential

This study assessed 34 strains of Enterococcus durans isolated from 8 samples of raw organic milk collected in both winter and summer seasons, with the aim of evaluating their technological capability. To achieve this, the following traits were tested: diacetyl production capability, autolysis capacity, organic acid production, expression of proteolytic and lipolytic enzymes, antagonistic capacity against pathogenic bacteria, as well as resistance to different types of antibiotics, hemolysin production, gelatinase production, and biofilm formation ability, as virulence factors. It was observed that 2.9% of the isolates exhibited the ability to produce diacetyl and showed proteolytic and autolytic capacity. Additionally, 8.8% displayed autolytic capacity, and 5.9% exhibited antagonistic capacity against Escherichia coli and Listeria monocytogenes, demonstrating that there are isolates with technological use potential.

Influence of pH on Oenococcus oeni metabolism: Can the slowdown of citrate consumption improve its acid tolerance?

Oenococcus oeni is the lactic acid bacteria most suited to carry out malolactic fermentation in wine, converting L-malic acid into L-lactic acid and carbon dioxide, thereby deacidifying wines. Indeed, wine is a harsh environment for microbial growth, partly because of its low pH. By metabolizing citrate, O. oeni maintains its homeostasis under acid conditions. Indeed, citrate consumption activates the proton motive force, helps to maintain intracellular pH, and enhances bacterial growth when it is co-metabolized with sugars. In addition, citrate metabolism is responsible for diacetyl production, an aromatic compound which bestows a buttery character to wine. However, an inhibitory effect of citrate on O. oeni growth at low pH has been highlighted in recent years. In order to understand how citrate metabolism can be linked to the acid tolerance of this bacterium, consumption of citrate was investigated in eleven O. oeni strains. In addition, malate and sugar consumptions were also monitored, as they can be impacted by citrate metabolism. This experiment highlighted the huge diversity of metabolisms between strains depending on their origin. It also showed the capacity of O. oeni to de novo metabolize certain end-products such as L-lactate and mannitol, a phenomenon never before demonstrated. It also enabled drawing hypotheses concerning the two positive effects that the slowing down of citrate metabolism could have on biomass production and malolactic fermentation occurring under low pH conditions.

Potential of Cheese-Associated Lactic Acid Bacteria to Metabolize Citrate and Produce Organic Acids and Acetoin.

Lactic acid bacteria (LAB) are pivotal in shaping the technological, sensory, and safety aspects of dairy products. The evaluation of proteolytic activity, citrate utilization, milk pH reduction, and the production of organic compounds, acetoin, and diacetyl by cheese associated LAB strains was carried out, followed by Principal Component Analysis (PCA). Citrate utilization was observed in all Leuconostoc (Le.) mesenteroides, Le. citreum, Lactococcus (Lc.) lactis, Lc. garvieae, and Limosilactobacillus (Lm.) fermentum strains, and in some Lacticaseibacillus (Lact.) casei strains. Most strains exhibited proteolytic activity, reduced pH, and generated organic compounds. Multivariate PCA revealed Le. mesenteroides as a prolific producer of acetic, lactic, formic, and pyruvic acids and acetoin at 30 °C. Enterococcus sp. was distinguished from Lact. casei based on acetic, formic, and pyruvic acid production, while Lact. casei primarily produced lactic acid at 37 °C. At 42 °C, Lactobacillus (L.) helveticus and some L. delbrueckii subsp. bulgaricus strains excelled in acetoin production, whereas L. delbrueckii subsp. bulgaricus and Streptococcus (S.) thermophilus strains primarily produced lactic acid. Lm. fermentum stood out with its production of acetic, formic, and pyruvic acids. Overall, cheese-associated LAB strains exhibited diverse metabolic capabilities which contribute to desirable aroma, flavor, and safety of dairy products.

Exploring the potential of Bacillus subtilis as cell factory for food ingredients and special chemicals

BackgroundBacillus subtilis has been established as model microorganism for fundamental research in the laboratory on protein production/secretion and sporulation and as model bacterium for controlling spoilage in the food industry. It has also been used for production of (commercial) enzymes and several secondary metabolites such as vitamins. However, this doesn’t fully reflect the potential of B. subtilis as a cell-factory. Here, various strains of B. subtilis, including food-grade, spore-deficient strains and industrially used strains, were compared for their growth and metabolic potential. Industry-relevant parameters were analyzed for all strains under various aeration regimes, under anaerobic conditions, in various nutritious and nutrient-limited cultivation media, with and without organic nitrogen sources, and with and without sugar.ResultsPractical experiments were conducted to compare industrial relevant properties like growth rates, intracellular components and extracellular metabolite profile of different B. subtilis strains. Based on growth flexibility in different media, we found that some strains like NCIB3610 and DSM1092 are adapted to inorganic or organic nitrogen source utilization, which is highly relevant when considering a biorefinery approach using various cheap and abundant waste/sidestreams. Secondly, spore-deficient strains such as 3NA, 168 S and PY79S, showed advantages in microbial protein and acetolactate pathway expression, which is associated with applications in food industry for protein supplement and diacetyl production. Lastly, WB800 and PY79S exhibited potential for fermentative production of dipicolinic acid, 2,3-butanediol and lactic acid that could serve as precursors for biopolymers.ConclusionThis study demonstrates the broad potential for more extensive industrial use of Bacillus subtilis in the (bio-based) chemical industry for use of sidestreams, in the personal care industry, in the food industry for food additive production, and in the bio-sustainable industry for biofuel and bio-degradable plastic precursors production. In addition, selecting different B. subtilis strains for specific purposes makes full use of the diversity of this species and increases the potential of B. subtilis in its contribution to the bio-based economy.

Bacteriocin and Antioxidant Production, a Beneficial Properties of Lactic Acid Bacteria Isolated from Fermented Vegetables of Northwest Bulgaria.

Lactiplantibacillus plantarum ST01BG, ST07BG, ST10BG, and ST15BG; Latilactobacillus curvatus ST02BG; Lacticaseibacillus paracasei ST04BG; Pediococcus pentosaceus ST05BG; Leuconostoc mesenteroides ST06BG; and Enterococcus faecium ST11BG were isolated from home-made fermented vegetables from Northwest Bulgaria and identified by biochemical, physiological, and biomolecular analyses, including partial 16S rRNA sequencing. The strains were designated as bacteriocin producers and the expressed antimicrobials partially characterized with a focus on their proteinaceous nature, stability to different pH and temperatures. The bacteriocins were effective in inhibiting different strains of Listeria spp., Enterococcus spp. (including vancomycin resistant enterococci) and Staphylococcus spp. These strains can be considered safe, based on the evaluation of hemolytic activity, production of biogenic amines, mucin degradation, antibiotic susceptibility/resistance, and gelatinase enzyme production. Moreover, the strains can be considered potentially beneficial based on their stability and survival under simulated gastrointestinal tract conditions (stomach and duodenum), the production of diacetyl, and specific levels of hydrophobicity. Special attention was given to antioxidant properties (DPPH radical, hydroxyl radical, superoxide anion radical scavenging activity, Fe+2 ion chelating activity, and anti-lipid peroxidation) of the strains. Antioxidant properties were found to be strain specific. The beneficial attributes (antimicrobial and antioxidant) of these cultures to fermented food products may enable the reduction of chemical additives in line with consumers' demand for more natural and chemical-free food commodities.

Leuconostoc performance in soy-based fermentations – Survival, acidification, sugar metabolism, and flavor comparisons

Leuconostoc spp. is often regarded as the flavor producer, responsible for the production of acetoin and diacetyl in dairy cheese. In this study, we investigate seven plant-derived Leuconostoc strains, covering four species, in their potential as a lyophilized starter culture for flavor production in fermented soy-based cheese alternatives. We show that the process of lyophilization of Leuconostoc can be feasible using a soy-based lyoprotectant, with survivability up to 63% during long term storage. Furthermore, the storage in this media improves the subsequent growth in a soy-based substrate in a strain specific manner. The utilization of individual raffinose family oligosaccharides was strain dependent, with Leuconostoc pseudomesenteroides NFICC99 being the best consumer. Furthermore, we show that all investigated strains were able to produce a range of volatile flavor compounds found in dairy cheese products, as well as remove certain dairy off-flavors from the soy-based substrate like hexanal and 2-pentylfuran. Also here, NFICC99 was strain producing most cheese-related volatile flavor compounds, followed by Leuconostoc mesenteroides NFICC319. These findings provide initial insights into the development of Leuconostoc as a potential starter culture for plant-based dairy alternatives, as well as a promising approach for generation of stable, lyophilized cultures.

Characterization and Functional Properties of Lactic Acid Bacteria Isolated from Fermented Maize Dough Used for the Preparation of Doklu

Lactic acid bacteria (LAB) has long been safely applied in the production of fermented foods and beverages. These bacteria are important for their contribution to food quality and also for their undeniable effects on health. In Africa, despite the abundance of isolated food sources and the diversity of identified microorganisms, the market for probiotics and functional foods based on selected local strains is almost non-existent. This paper aims to determine some technological properties of LAB isolates from fermented maize dough used for doklu production for potential application in food and probiotic products. A total of 25 LAB strains isolated from maize dough fermentation processes during doklu production were identified by 16S rDNA gene sequencing. Technological studies such as growth and acidification kinetics, diacetyl production, hydrogen peroxide production, and proteolytic activity were carried out. Their survival and growth under unfavorable conditions of temperature, salt concentration and pH were also analyzed. The isolates were identified as Pediococcus acidilactici (56%), Lactobacillus fermentum (24%), Pediococcus pentosaceus (12%) and Lactobacillus plantarum (8%). The technological properties of the LAB strains showed that 10 of them rapidly acidify the medium with pH variation (ΔpH) greater than 1 after 6 hours of fermentation. Good production of diacetyl and hydrogen peroxide, as well as good proteolytic activity, were obtained for several strains. Pediococcus acidilactici S15, S55, S56; Lactobacillus plantarum S32, S121 and Lactobacillus fermentum S44 showed the best technological properties. However, only 5 of them obtained good resistance following the various survival and growth under unfavorable conditions of temperature, salt concentration, and pH. This work has therefore demonstrated that the lactic acid bacteria involved in the natural fermentation of maize dough have interesting properties for various applications whether in the processing of food products as well as in the development of probiotic products.

A potential probiotic Enterococcus faecium isolated from camel rumen, fatty acids biotransformation, antilisteria activity and safety assessment

The probiotic features of a new Enterococcus faecium strain isolated from camel rumen were investigated. The isolate identified as E. faecium 96B4 exhibited notable tolerance to gastrointestinal conditions, with high cell viability at pH 1.5 after 3 h (about 7.48 log10 cfu mL−1). Besides complete inhibition of Listeria monocytogenes growth, E. faecium 96B4 showed high hydrophobicity, auto- and co-aggregations abilities. It showed 76.33% cholesterol assimilation ability and boosted the extracellular unsaturated fatty acid content up to 25.53% in the presence of soybean oil as a substrate. Moreover, 96.17 ± 3.52 μg mL−1 conjugated linoleic acid production and 2.56 fold increase in oleic acid content were highlighted. Significant diacetyl production ability was also demonstrated. E. faecium 96B4 passed the safety assessment successfully. The association between the microbiome and host health makes the camel, as a unique animal, a rich source of beneficial microorganism candidates for designing future foods.

Technological Characterization of Lactic Acid Bacteria Strains for Potential Use in Cheese Manufacture.

A total of 26 lactic acid bacteria isolates from both Italian and Brazilian cheeses were tested for their use in cheesemaking. Isolates were screened for salt tolerance, exopolysaccharide and diacetyl production, lipolytic, acidifying, and proteolytic activities. In addition, the aminopeptidase (Pep N and Pep X) activities, were evaluated. Most of the strains demonstrated salt tolerance to 6% of NaCl, while only two L. delbruekii (P14, P38), one L. rhamnosus (P50) and one L. plantarum (Q3C4) were able to grow in the presence of 10% (w/v) of NaCl. Except for 2 L. plantarum (Q1C6 and Q3C4), all strains showed low or medium acidifying activity and good proteolytic features. Furthermore, lipolytic activity was revealed in none of the strains, while the production of EPS and diacetyl was widespread and variable among the tested strains. Finally, regarding aminopeptidase activities, 1 L. delbrueckii (P10), 1 L. rhamnosus (P50), and 1 L. lactis (Q5C6) were considered as the better performing, showing high values of both Pep N and Pep X. Based on data presented here, the aforementioned strains could be suggested as promising adjunct cultures in cheesemaking.

Evaluation of Antibacterial Activity of Lactic Acid Bacteria Isolated from Kunun Zaki against Selected Bread Rope Spoilage Bacteria

In line with increasing demand by consumers for safe and minimally processed food products, biopreservation has been advocated over the traditional use of chemical additives in combating food spoilage. This study evaluated the antibacterial activity of four lactic acid bacteria (LAB) (Lactobacillus fermentum, Lactococcus lactis, Lactobacillus brevis and Lactobacillus plantarum) isolated from kunun-zaki against the bread rope spoilage bacteria, Bacillus subtilis and Bacillus cereus. Antibacterial activity was determined using the dual agar overlay method with subsequent measurement of zones of inhibition. Titrimetric methods were used to determine the abilities of the isolated LAB to produce antimicrobials including lactic acid, hydrogen peroxide and diacetyl. Lactobacillus fermentum brought about the highest inhibition zone (20 mm) against Bacillus cereus. The smallest zone of inhibition (6 mm) was recorded for L. plantarum against B. cereus. Whereas L. plantarum produced the highest amount of lactic acid (0.540 g/L), L. brevis produced the lowest lactic acid amount of 0.348 g/L. L. fermentum produced the highest amount of hydrogen peroxide (0.020 g/L) whereas L.brevis recorded the lowest hydrogen peroxide production of 0.010 g/L. L. lactis and L. fermentum had the highest and lowest values of 0.649 g/L and 0.219 g/L respectively for diacetyl production. Differences in the antibacterial activities and antimicrobials production by the LAB were statistically significant (P < .05). The findings show that the LAB isolates possessed antibacterial activity against the selected spoilage bacteria and as such could be exploited as potential biocontrol agents against the selected bread rope spoilage bacteria.

Development of a novel lactic acid bacteria starter culture approach: From insect microbiome to plant-based fermentations

Lactic acid bacteria (LAB) are a broad group of gram-positive bacteria that have actively been used worldwide in food productions due to their nutritional, technological, bioprotection and flavour-related characteristics, which define them as powerful biological tools to be used in fermented food applications. LAB are ubiquitous in nature and some species have been found in fructose-rich niches, such as insect microbiomes. Twenty-eight LAB species were isolated from Apis mellifera, Bombus spp. and Andrena nigroaenea insect sources. Lactococcus lactis was the most widespread species in all insect species. A phenotypical characterization analysis based on carbohydrate metabolism, subproduct and acid production, pectinolytic activity, citrate uptake, phytate degradation and diacetyl production was carried out. Based on this analysis, two strains belonging to Leuconostoc pseudomesenteroides and L.lactis species were found to be the most suitable strains for use in common food plant matrices. The former showed an ability to significantly catabolize raffinose, maltose and citrate, which are present in soy beverages, while the latter was able to produce high concentrations of diacetyl and lactic acid, which are relevant for the generation of plant dairy alternatives, and noticeably degraded phytic acid, pectin and sucrose mostly found in bean, cereal and fruit-based plant matrices.

Investigation of the probiotic and metabolic potential of Fructobacillus tropaeoli and Apilactobacillus kunkeei from apiaries.

Honeybee products have been among important consumer products throughout history. Microbiota has attracted attention in recent years due to both their probiotic value and industrial potential. Fructophilic lactic acid bacteria (FLAB), whose field of study has been expanding rapidly in the last 20 years, are among the groups that can be isolated from the bee gut. This study aimed to isolate FLAB from the honeybees of two different geographic regions in Turkey and investigate their probiotic, metabolic and anti-quorum sensing (anti-QS) potential. Metabolic properties were investigated based on fructose toleration and acid and diacetyl production while the probiotic properties of the isolates were determined by examining pH, pepsin, pancreatin resistance, antimicrobial susceptibility, and antimicrobial activity. Anti-QS activities were also evaluated with the Chromobacterium violaceum biosensor strain. Two FLAB members were isolated and identified by the 16S rRNA analysis as Fructobacillus tropaeoli and Apilactobacillus kunkeei, which were found to be tolerant to high fructose, low pH, pepsin, pancreatin, and bile salt environments. Both isolates showed anti-QS activity against the C. violaceum biosensor strain and no diacetyl production. The daily supernatants of the isolates inhibited the growth of Enterococcus faecalis ATCC 29212 among the selected pathogens. The isolates were found resistant to kanamycin, streptomycin, erythromycin, and clindamycin. In the evaluation of the probiotic potential of these species, the negative effect of antibiotics and other chemicals to which honeybees are directly or indirectly exposed draws attention within the scope of the "One Health" approach.

Characterization of autochthonous lactic acid bacteria in Bom Jesus do Itabapoana (Brazil): antagonist action against Listeria monocytogenes and biochemical evidences

Lactic Acid Bacteria (LAB) are used in the elaboration of industrial and artisanal dairy and fermented products, and have a wide diversification, which can influence the characterization of the products and guarantee food safety. The present work aims to isolate and characterize autochthonous LAB from Bom Jesus do Itabapoana (Brazil), from raw milk and artisanal fresh cheese, verifying their antagonistic potential against L. monocytogenes, diacetyl production and the profile of lacto-fermentation. For isolation, the MRS and M17 media were used, incubated at 37 ºC and 30 ºC for 48 h, respectively. Ten strains that showed characteristics for LAB were evaluated for antagonistic action against the pathogen, production of diacetyl and profile of lacto-fermentation. Seven of them showed antagonistic action, diacetyl production and caseous lacto-fermentation, while three did not show antagonistic action and diacetyl production, however one maintained the caseous lacto-fermentation type and two presented gelatinous type.

Technological characterization and antibacterial activity of Lactococcus lactis subsp. cremoris strains for potential use as starter culture for cheddar cheese manufacture

Several technological applications of Lactococcus lactis are attributed to their high metabolite-secreting abilities. Among these, bacteriocins can be used as food preservatives or additives in cheese manufacture. The objective was to evaluate the technological characteristics and antibacterial activity of 10 Lactococcus lactis isolates from traditional fermented dairy products, including acidifying ability, proteolytic ability, diacetyl production and autolytic activity. L. lactis subsp. cremoris Y14 and Y15 showed significantly (P < 0.05) higher ΔpH than other strains. L. lactis subsp. cremoris Y17 exhibited the highest proteolytic, L. lactis subsp. cremoris Y15 and L. lactis subsp. cremoris Y18 were next in terms of proteolytic activity. All strains possessed the ability of diacetyl production, with the highest production of 10.39 mg/g observed in L. lactis subsp. cremoris Y15. L. lactis subsp. cremoris Y14 had the highest (P < 0.05) autolytic ability (8.96%), followed by L. lactis subsp. cremoris Y15 (8.05%). L. lactis Y15 exhibited discernible antibacterial activity with the largest zone of inhibition diameters (25.56 mm). Based on the above results, L. lactis subsp. cremoris Y15 was selected as the starter to manufacture cheese. There were no significant differences in texture and sensory acceptability of Cheddar cheese manufactured by L. lactis subsp. cremoris Y15 with L. lactis subsp. lactis KLDS4.0325 or commercial starter. L. lactis subsp. cremoris Y15 can be used as a starter to produce Cheddar cheese.

Optimal Design Approach Applied to Headspace GC for the Monitoring of Diacetyl Concentration, Spectrophotometric Assessment of Phenolic Compounds and Antioxidant Potential in Different Fermentation Processes of Barley

The present study aimed to validate a control method on the gas chromatography system (GC) based on the experimental design strategy, to examine the changes and correlation between the fermentation process and the quality of alcoholic and non-alcoholic beer product, especially the formation of diacetyl. On the other hand, spectrophotometric methods were applied to the determination of polyphenols content and the potential antioxidant activity of beer during different fermentation processes. with this aim, three modes of barley fermentation were used, specifically classical fermentation, stopped fermentation and thermal process. The results showed that the different fermentation modes had a major impact on diacetyl production. The highest concentration was obtained using stopped fermentation 0.36 mg/L, the lowest concentration value 0.07 mg/L was detected using the thermal process. Monitoring the increase of oxygen concentration between fermentation, filtration, and filling of the final product (32, 107, 130 ppm, respectively) has a significant impact on the concentration of diacetyl. The obtained results of spectrophotometric analysis showed that the total antioxidant activity changed during beer fermentation process and demonstrate that the extend of the antioxidant activity was very much dependent on the total polyphenolic content with a higher value in Hopped wort (13.41%, 65 mg GAE 100 mL−1, 28 mg CE 100 mL−1) for antioxidant potential, total phenolic content, and total flavonoids content, respectively, whereas the lowest values was detected in Non-alcoholic beer using thermal process (7.24%, 35 mg GAE 100 mL−1, 10 mg CE 100 mL−1) for antioxidant potential, total phenolic contents, and total flavonoids contents, respectively. Based on the results achieved, we reveal the impact of the fermentation process on the nutritional value of the final product.

Genomic, biochemical and microbial evaluation of probiotic potentials of bacterial isolates from fermented sorghum products

Fermented products, including Ogi-baba and Pito, provide several health benefits, particularly when probiotics are used in the fermentation process. Probiotic microorganisms exert strain-specific health-promoting activities on humans and animals. The objective of this study was to investigate the probiotic potentials of Lactic-acid bacteria (LAB) isolates from indigenous fermented sorghum products (Ogi-baba and Pito). The LAB isolates were screened for potential probiotic properties by antagonistic activity against eight enteropathogenic clinical bacteria isolates (Escherichia coli, Klebsiella sp., Helicobacter pylori, Bacillus sp., Staphylococcus sp., Salmonella sp., Pseudomonas sp. and Listeria monocytogenes) as indicator organisms using the agar well diffusion technique. The organisms were also screened for acidity, bile tolerance, antibiotic susceptibility, production of lactic acid, diacetyl and hydrogen peroxide. β-galactosidase assay was also done. Genomic DNA was extracted from the two selected LAB isolates; the 16S rRNA were amplified and sequenced. The sequence data were subjected to Basic Local Alignment Search Tool (BLAST) and molecular phylogenetic analyses to identify the isolates. The isolates were identified as strains of Lactobacillus plantarum and Pediococcus pentosaceus. The sequence data for these two isolates were submitted to the Genbank with accession numbers KP883298 and KP883297 respectively. The P. pentosaceus strain (PB2) strain exhibited β-galactosidase activity as well as L. plantrum strain (OB6). The study revealed exceptional probiotic potentials of two LAB namely Lactobacillus plantarum strain (OB6) and Pediococcus pentosaceus strain (PB2) isolated from fermented sorghum products, Ogi-baba and Pito respectively. Hence, the two LAB strains may be potentially used as probiotic to prevent some enteropathogen-induced gastrointestinal disorders; reduce the incidence of respiratory tract infections and for the management of lactose in intolerance.

Potential for Lager Beer Production from Saccharomyces cerevisiae Strains Isolated from the Vineyard Environment

Saccharomyces pastorianus, genetic hybrids of Saccharomyces cerevisiae and the Saccharomyces eubayanus, is one of the most widely used lager yeasts in the brewing industry. In recent years, new strategies have been adopted and new lines of research have been outlined to create and expand the pool of lager brewing starters. The vineyard microbiome has received significant attention in the past few years due to many opportunities in terms of biotechnological applications in the winemaking processes. However, the characterization of S. cerevisiae strains isolated from winery environments as an approach to selecting starters for beer production has not been fully investigated, and little is currently available. Four wild cryotolerant S. cerevisiae strains isolated from vineyard environments were evaluated as potential starters for lager beer production at laboratory scale using a model beer wort (MBW). In all tests, the industrial lager brewing S. pastorianus Weihenstephan 34/70 was used as a reference strain. The results obtained, although preliminary, showed some good properties of these strains, such as antioxidant activity, flocculation capacity, efficient fermentation at 15 °C and low diacetyl production. Further studies will be carried out using these S. cerevisiae strains as starters for lager beer production on a pilot scale in order to verify the chemical and sensory characteristics of the beers produced.