Strains Of Acetic Acid Bacteria Research Articles

Oxidative fermentation of glucose and ethanol in designed media and cooked grape must by acetic acid bacteria

In this study, acetic acid bacteria strains were investigated for their ability to oxidize different carbon sources producing the corresponding oxidative products. Bacterial strains were cultivated in seven designed media and their acetification ability was assessed. The most performing strains were further tested to evaluate gluconic acid production in cooked grape must. Organic acids, sugars, and ethanol concentrations were assayed by high-pressure liquid chromatography. Overall, the findings showed high variability amongst strains of the same species, especially amongst Gluconobacter oxydans strains. However, strains ATCC 621H and DSM 3503T resulted to be the highest gluconic acid producers in all tested conditions. This study shows that grape must can be further valorized by selective fermentations for the production of gluconic based products.

Novel Gluconobacter oxydans strains selected from Kombucha with potential postbiotic activity

Gastric and colorectal cancer are among the most frequently diagnosed malignancies of the gastrointestinal tract. Searching for methods of therapy that complements treatment or has a preventive effect is desirable. Bacterial metabolites safe for human health, which have postbiotic effect, are of interest recently. The study aimed to preliminary assessment of the safety, antimicrobial, and anti-cancer activity of cell-free metabolites of Gluconobacter oxydans strains isolated from Kombucha beverages as an example of the potential postbiotic activity of acetic acid bacteria (AAB). The study material consisted of five AAB strains of Kombucha origin and three human cell lines (gastric adenoma—AGS, colorectal adenoma—HT-29, and healthy cells derived from the endothelium of the human umbilical vein—HUVEC). Results of the study confirms the health safety and functional properties of selected AAB strains, including their potential postbiotic properties. The best potential anticancer activity of the AAB cell-free supernatants was demonstrated against AGS gastric adenoma cells. The conducted research proves the postbiotic potential of selected acetic acid bacteria, especially the KNS30 strain.Key points•The beneficial and application properties of acetic acid bacteria are poorly studied.•Gluconobacter oxydans from Kombucha show a postbiotic activity.•The best anticancer activity of the G. oxydans showed against gastric adenoma.

Screening of Acetic Acid Bacteria Isolated from Various Sources for Use in Kombucha Production

The objective of this study was to isolate and identify strains of Acetobacter suitable for use in the development of a complex microbial culture for producing Kombucha and to examine the fermentation characteristics for selection of suitable strains. A medium supplemented with calcium carbonate was used for isolation of acetic acid bacteria from 22 various sources. Colonies observed in the clear zone resulting from decomposition of calcium carbonate by acid produced by microorganisms were collected. Identification of the collected strains was based on biological and morphological characteristics, and the results of base sequence analysis. A total of 37 strains were identified, including six species in the Acetobacter genus: Acetobacter pasteurianus, Acetobacter orientalis, Acetobacter cibinongensis, Acetobacter pomorum, Acetobacter ascendens, and Acetobacter malorum, as well as one species in the Gluconobacter genus, Gluconobacter oxydans. Among thirty-seven strains, seven strains of acetic acid bacteria with exceptional acid and alcohol tolerance were selected, and an evaluation of their fermentation characteristics according to fermentation temperature and period was performed. The results showed a titratable acidity of 1.68% for the Acetobacter pasteurianus SFT-18 strain, and an acetic acid bacteria count of 9.52 log CFU/mL at a fermentation temperature of 35 °C. The glucuronic acid and gluconate contents for the Gluconobacter oxydans SFT-27 strain were 10.32 mg/mL and 25.49 mg/mL, respectively.

Selection of Thermotolerant and Non Overoxydative Acetic Acid Strains for Cost Effective Vinegar Production

The aim of this study was to select thermotolerant acetic acid bacteria with no overoxidation ability that would be useful for low-cost vinegar production. Acetic bacteria were isolated from palm wine and mango pulp after 3 to 5 days of fermentation. The isolates were first characterized by biochemical tests and were identified by sequencing of the rRNA 16 S gene. From the substrates collected, a total of 48 acetic acid bacteria were isolated. Among them, 8 strains showing inability to oxidate acetate to CO2 and H2O. Three strains of these 8 isolates belonging to Gluconobacter oxydans (Ski1) and to Acetobacter ghanensis (Fke 22 and Fk5) were able to grow and produce acetic acid at 37°C and in culture medium containing 5% of ethanol and until 10% of acetic acid. This study allows to select three thermotolerant acetic acid bacteria strains with high amount of acetic acid production capacity but with no-overoxydation ability. These strains could then be useful as starters for low-cost vinegar production.

Production efficiency and properties of bacterial cellulose membranes in a novel grape pomace hydrolysate by Komagataeibacter melomenusus AV436T and Komagataeibacter xylinus LMG 1518

The microbial production of cellulose using different bacterial species has been extensively examined for various industrial applications. However, the cost-effectiveness of all these biotechnological processes is strongly related to the culture medium for bacterial cellulose (BC) production. Herein, we examined a simple and modified procedure for preparing grape pomace (GP) hydrolysate, without enzymatic treatment, as a sole growth medium for BC production by acetic acid bacteria (AAB). The central composite design (CCD) was used to optimise the GP hydrolysate preparation toward the highest reducing sugar contents (10.4 g/L) and minimal phenolic contents (4.8 g/L). The experimental screening of 4 differently prepared hydrolysates and 20 AAB strains identified the recently described species Komagataeibacter melomenusus AV436T as the most efficient BC producer (up to 1.24 g/L dry BC membrane), followed by Komagataeibacter xylinus LMG 1518 (up to 0.98 g/L dry BC membrane). The membranes were synthesized in only 4 days of bacteria culturing, 1 st day with shaking, followed by 3 days of static incubation. The produced BC membranes in GP-hydrolysates showed, in comparison to the membranes made in a complex RAE medium 34 % reduction of crystallinity index with the presence of diverse cellulose allomorphs, presence of GP-related components within the BC network responsible for the increase of hydrophobicity, the reduction of thermal stability and 48.75 %, 13.6 % and 43 % lower tensile strength, tensile modulus, and elongation, respectively. Here presented study is the first report on utilising a GP-hydrolysate without enzymatic treatment as a sole culture medium for efficient BC production by AAB, with recently described species Komagataeibacter melomenusus AV436T as the most efficient producer in this type of food-waste material. The scale-up protocol of the scheme presented here will be needed for the cost-optimisation of BC production at the industrial levels.

Obtaining Bacterial Cellulose through Selected Strains of Acetic Acid Bacteria in Classical and Waste Media

Bacterial cellulose (BC) is a natural exopolysaccharide characterized by a high purity, mechanical strength, and the ability to absorb various compounds. Obtaining BC on an industrial scale is expensive, mainly due to the high cost of the culture media. Replacing classical media with waste from the agri-food industry may be a promising way to reduce the costs when obtaining BC. The aim of these studies was to compare the effectiveness of the biosynthesis of BC in classical and waste media using two strains, Komagataeibacter xylinus K2G30 and Gluconacetobacter hansenii ATCC 23769. Classical Hestrin−Schramm, YPM, GY, and GYE media were used. The waste media were banana peels, celery pomace, fish waste, hemp seed pomace, deproteinized acid whey (DAW), and non-deproteinized acid whey (NDAW). The highest efficiency of BC biosynthesis in classical media was observed in YPM and it was 5.23 g·dm−3 with K. xylinus K2G30. In the waste media, the highest yield of BC was observed in AW, when the yield of BC was 2.99 g·dm−3 with K. xylinus K2G30. In addition, it was demonstrated that the presence of proteins and lactic acid in AW influenced the efficiency when obtaining BC in the culture of K. xylinus. The results indicate that it is possible to obtain BC from industrial waste, especially from AW.

Draft Genome Sequences of Three Type Strains, Acetobacter farinalis KACC 21251, Acetobacter suratthaniensis KACC 21252, and Acetobacter thailandicus KACC 21253.

As part of a genome database construction of type strains, we report the draft genome sequences of three strains of acetic acid bacteria, i.e., Acetobacter farinalis KACC 21251T, Acetobacter suratthaniensis KACC 21252T, and Acetobacter thailandicus KACC 21253T.

Acetic acid bacteria in agro-wastes: from cheese whey and olive mill wastewater to cellulose

In this study, cheese whey and olive mill wastewater were investigated as potential feedstocks for producing bacterial cellulose by using acetic acid bacteria strains. Organic acids and phenolic compounds composition were assayed by high-pressure liquid chromatography. Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction were used to investigate modifications in bacterial cellulose chemical and morphological structure. Cheese whey was the most efficient feedstock in terms of bacterial cellulose yield (0.300g of bacterial cellulose/gram of carbon source consumed). Bacterial cellulose produced in olive mill wastewater presented a more well-defined network compared to pellicles produced in cheese whey, resulting in a smaller fiber diameter in most cases. The analysis of bacterial cellulose chemical structure highlighted the presence of different chemical bonds likely to be caused by the adsorption of olive mill wastewater and cheese whey components. The crystallinity ranged from 45.72 to 80.82%. The acetic acid bacteria strains used in this study were characterized by 16S rRNA gene sequencing, allowing to assign them to Komagataeibacter xylinus and Komagataeibacter rhaeticus species. This study proves the suitability to perform sustainable bioprocesses for producing bacterial cellulose, combining the valorisation of agro-wastes with microbial conversions carried out by acetic acid bacteria. The high versatility in terms of yield, morphology, and fiber diameters obtained in cheese whey and olive mill wastewater contribute to set up fundamental criteria for developing customized bioprocesses depending on the final use of the bacterial cellulose. KEY POINTS: • Cheese whey and olive mill wastewater can be used for bacterial cellulose production. • Bacterial cellulose structure is dependent on the culture medium. • Komagataeibacter strains support the agro-waste conversion in bacterial cellulose.

Effects of different acetic acid bacteria strains on the bioactive compounds, volatile compounds and antioxidant activity of black tea vinegar

This study intends to produce a black tea vinegar (BTV) from low-quality bulk black tea in order to increase its consumption and added value, and to benefit from its functional characteristics. Three strains (Acetobacter sp. GDMCC1.152, Acetobacter pasteurianus GDMCC1.67, and Acetobacter aceti ATCC15973) of acetic acid bacteria (AAB) were inoculated into black tea infusion (BTI) with ethanol to produce BTV, and their effects on bioactive compounds, antioxidant activity, and volatile compounds in the vinegars were revealed. The results showed that the three strains were suitable for the production of BTV, and the vinegar quality was the best after acetic acid fermentation for 6 days. Compared with BTI, the contents of organic acids and volatile compounds and the antioxidant activity of the vinegars increased significantly. Among them, the vinegar produced by GDMCC1.152 strain had the highest content of organic acids, tea polyphenols (TPs), thearubigins (TRs), theabrownines (TBs), and volatile compounds. It also possessed the strongest antioxidant activity and a rich taste with an apple-like aroma. In summary, AAB fermentation can effectively improve the flavor and quality of BTI and produce a new healthy product with high activity, and Acetobacter sp. GDMCC1.152 is the most suitable strain for the production of BTV.

RNA-Seq transcriptomic analysis reveals gene expression profiles of acetic acid bacteria under high-acidity submerged industrial fermentation process.

Acetic acid bacteria (AAB) are Gram-negative obligate aerobics in Acetobacteraceae family. Producing acetic acid and brewing vinegars are one of the most important industrial applications of AAB, attributed to their outstanding ability to tolerate the corresponding stresses. Several unique acid resistance (AR) mechanisms in AAB have been revealed previously. However, their overall AR strategies are still less-comprehensively clarified. Consequently, omics analysis was widely performed for a better understanding of this field. Among them, transcriptome has recently obtained more and more attention. However, most currently reported transcriptomic studies were conducted under lab conditions and even in low-acidity environment, which may be unable to completely reflect the conditions that AAB confront under industrialized vinegar-brewing processes. In this study, we performed an RNA-Seq transcriptomic analysis concerning AAB’s AR mechanisms during a continuous and periodical industrial submerged vinegar fermentation process, where a single AAB strain performed the fermentation and the acetic acid concentration fluctuated between ~8% and ~12%, the highest acidity as far we know for transcriptomic studies. Samples were directly taken from the initial (CK), mid, and final stages of the same period of the on-going fermentation. 16S rRNA sequence analysis indicated the participation of Komagataeibacter europaeus in the fermentation. Transcriptomic results demonstrated that more genes were downregulated than upregulated at both mid and final stages. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrich analysis reflected that the upregulated genes mainly carried out tricarboxylic acid cycle and oxidative phosphorylation processes, probably implying a considerable role of acetic acid overoxidation in AR during fermentation. Besides, upregulation of riboflavin biosynthesis pathway and two NAD+-dependent succinate-semialdehyde dehydrogenase-coding genes suggested a critical role of succinate oxidation in AR. Meanwhile, downregulated genes were mainly ribosomal protein-coding ones, reflecting that the adverse impact on ribosomes initiates at the transcription level. However, it is ambiguous whether the downregulation is good for stress responding or it actually reflects the stress. Furthermore, we also assumed that the fermentation stages may have a greater effect on gene expression than acidity. Additionally, it is possible that some physiological alterations would affect the AR to a larger extent than changes in gene expression, which suggests the combination of molecular biology and physiology research will provide deeper insight into the AR mechanisms in AAB.

Screening and Characterization of New Acetobacter fabarum and Acetobacter pasteurianus Strains with High Ethanol−Thermo Tolerance and the Optimization of Acetic Acid Production

The production of vinegar on an industrial scale from different raw materials is subject to constraints, notably the low tolerance of acetic acid bacteria (AAB) to high temperatures and high ethanol concentrations. In this study, we used 25 samples of different fruits from seven Moroccan biotopes with arid and semi-arid environmental conditions as a basic substrate to isolate thermo- and ethanol-tolerant AAB strains. The isolation and morphological, biochemical and metabolic characterization of these bacteria allowed us to isolate a total number of 400 strains with characters similar to AAB, of which six strains (FAGD1, FAGD10, FAGD18 and GCM2, GCM4, GCM15) were found to be mobile and immobile Gram-negative bacteria with ellipsoidal rod-shaped colonies that clustered in pairs and in isolated chains. These strains are capable of producing acetic acid from ethanol, growing on peptone and oxidizing acetate to CO2 and H2O. Strains FAGD1, FAGD10 and FAGD18 show negative growth on YPG medium containing D-glucose > 30%, while strains GCM2, GCM4 and GCM15 show positive growth. These six strains stand out on CARR indicator medium as isolates of the genus Acetobacter ssp. Analysis of 16S rDNA gene sequencing allowed us to differentiate these strains as Acetobacter fabarum and Acetobacter pasteurianus. The study of the tolerance of these six isolates towards pH showed that most of the six strains are unable to grow at pH 3 and pH 9, with an ideal pH of 5. The behavior of the six strains at different concentrations of ethanol shows an optimal production of acetic acid after incubation at concentrations between 6% and 8% (v/v) of ethanol. All six strains tolerated an ethanol concentration of 16% (v/v). The resistance of the strains to acetic acid differs between the species of AAB. The optimum acetic acid production is obtained at a concentration of 1% (v/v) for the strains of FAGD1, FAGD10 and FAGD18, and 3% (v/v) for GCM2, GCM4 and GCM15. These strains are able to tolerate an acetic acid concentration of up to 6% (v/v). The production kinetics of the six strains show the highest levels of growth and acetic acid production at 30 °C. This rate of growth and acetic acid production is high at 35 °C, 37 °C and 40 °C. Above 40 °C, the production of acid is reduced. All six strains continue to produce acetic acid, even at high temperatures up to 48 °C. These strains can be used in the vinegar production industry to minimize the load on cooling systems, especially in countries with high summer temperatures.

Nutritional Supplementation with Amino Acids on Bacterial Cellulose Production by Komagataeibacter intermedius: Effect Analysis and Application of Response Surface Methodology.

Bacterial cellulose (BC) is a biopolymer mainly produced by acetic acid bacteria (AAB) that has several applications in the medical, pharmaceutical, and food industries. As other living organisms, AAB require sources of chemical elements and nutrients, which are essential for their multiplication and metabolite production. So, the knowledge of the nutritional needs of microorganisms that have important industrial applications is necessary for the nutrients to be supplied in the appropriate form and amount. Considering that the choice of different nutrients as nitrogen source can result in different metabolic effects, this work aimed to verify the effects of amino acid supplementation in the culture media for BC production by an AAB strain (Komagataeibacter intermedius V-05). For this, nineteen amino acids were tested, selected, and optimized through a Plackett and Burman factorial design and central composite design to determine the optimal concentrations of each required amino acid. Membranes produced under optimal conditions were characterized in relation to chemical structure and properties by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared spectroscopy (FT-IR), and hydrophilic properties. Three amino acids had a significant positive effect and were required: aspartic acid (1.5g L-1), phenylalanine (1.5g L-1), and serine (3.0g L-1). Conversely, all sulfur and positively charged amino acids had a negative effect and reduced the production yield. After optimization and validation steps, a production level of 3.02g L-1 was achieved. Membranes produced from optimized media by this strain presented lower crystallinity index but greater thermal and hydrophilic properties than those produced from standard HS medium.

Oxidative Fermentation of Acetic Acid Bacteria and Its Products.

Acetic acid bacteria (AAB) are a group of Gram-negative, strictly aerobic bacteria, including 19 reported genera until 2021, which are widely found on the surface of flowers and fruits, or in traditionally fermented products. Many AAB strains have the great abilities to incompletely oxidize a large variety of carbohydrates, alcohols and related compounds to the corresponding products mainly including acetic acid, gluconic acid, gulonic acid, galactonic acid, sorbose, dihydroxyacetone and miglitol via the membrane-binding dehydrogenases, which is termed as AAB oxidative fermentation (AOF). Up to now, at least 86 AOF products have been reported in the literatures, but no any monograph or review of them has been published. In this review, at first, we briefly introduce the classification progress of AAB due to the rapid changes of AAB classification in recent years, then systematically describe the enzymes involved in AOF and classify the AOF products. Finally, we summarize the application of molecular biology technologies in AOF researches.

Candidate Acetic Acid Bacteria Strains for Levan Production.

In this study, twelve strains of acetic acid bacteria (AAB) belonging to five different genera were tested for their ability to produce levan, at 70 and 250 g/L of sucrose concentration, respectively. The fructan produced by the bacterial strains was characterized as levan by NMR spectroscopy. Most of the strains produced levan, highlighting intra- and inter-species variability. High yield was observed for Neoasaia chiangmaiensis NBRC 101099 T, Kozakia baliensis DSM 14400 T and Gluconobacter cerinus DSM 9533 T at 70 g/L of sucrose. A 12-fold increase was observed for N. chiangmaiensis NBRC 101099 T at 250 g/L of sucrose concentration. Levan production was found to be affected by glucose accumulation and pH reduction, especially in Ko. baliensis DSM 14400 T. All the Gluconobacter strains showed a negative correlation with the increase in sucrose concentration. Among strains of Komagataeibacter genus, no clear effect of sucrose on levan yield was found. Results obtained in this study highlighted the differences in levan yield among AAB strains and showed interdependence between culture conditions, carbon source utilization, and time of incubation. On the contrary, the levan yield was not always related to the sucrose concentration.

농가형 발효식초로부터 분리한 초산균 6종의 배양 및 기능적 특성 규명

The present study evaluated the cultural and functional characteristics of six strains of acetic-acid bacteria (AAB), namely, GHUR-A11-2, SR-A24, GY-A26, GHF-A37, JS-B7, and JS-C1, which were isolated from farm-made fermented vinegars. The six bacterial strains exhibited high acetic acid production capability via the decomposition of CaCO3, and they were identified as Acetobacter pasteurianus based on the 16S rDNA sequences. The initial pH and optimal growth temperature for acetic acid production were determined to be 4.0 and 30°C, respectively; however, some strains of AAB presented reasonable growth even at 40°C. Four bacterial strains (except SR-A24 and GHF-A37) exhibited alcohol degradation activities of more than 90%. Bacillus cereus presented high susceptibility to the antibacterial activity of the six strains of AAB. The antioxidant activity evaluated using DPPH and ABTS was 5–15 times and 4–5 times higher for the six strains of AAB than that for the control group, respectively. GHUR-A11-2, SR-A24, and JS-C1 exhibited higher ACE activities, with inhibition rates of 154%-175%, as compared to those exhibited by the positive control of 0.1% captopril (inhibition rate of 138%). Furthermore, the fibrinolysis activity of SR-A24 (93.3%) was markedly higher than that of 0.5 U plasmin. Four bacterial strains (except GHF-A37 (75.3%) and JS-B7 (68.0%)), exhibited α-glucosidase inhibition activities of more than 100%. It was concluded that the six strains of AAB exhibited excellent physiologically active characteristics, which facilitated their use as seed strains for the synthesis of high-efficiency functional vinegar by harnessing the functional characteristics that fit the scientific basis.

Thermoresistant, Ethanol-Resistant and Acid-Resistant Properties of Acetic Acid Bacteria Isolated from Fermented Mango Alcohol

Vinegar production is seriously affected by the sensitivity of acetic acid bacteria (AAB) to high temperature, high ethanol concentrations, and high acetic acid concentrations. The aim of this study was to investigate the thermo-ethanol-acid tolerance characters of five AAB strains (VMA1, VMA5, VMA7, VMAM, VMAO) previously isolated from fermented mango alcohol and belonging to Gluconoacetobacter genera. As result, the five AAB strains exhibited good growth and acid production at temperatures up to 45°C; they could tolerate and produce acetic acid at ethanol concentrations up to 20% (v/v). In addition, the studied strains showed growth at acetic acid concentrations up to 4.5% (w/v). Strains VMA7 and VMAO showed the highest resistance properties: they demonstrated acid production at 50°C and VMAO could even grow at 60°C; they tolerated and produced acetic acid at 25% (v/v) ethanol concentration; they showed resistance to acetic acid concentrations up to 6% (w/v). Considering all these properties, the use of these strains would seriously contribute to improving the quality of the vinegar produced and help to reduce the cooling water feeds in vinegar production especially in hot countries in the context of global warming.

Inoculation with acetic acid bacteria improves the quality of natural green table olives

This study aims to develop a method for the preparation of natural table olives using locally selected microorganisms and without resorting to the usual techniques which employ lye treatment and acids. The effects of parameters, such as lye treatment, inoculation with yeasts, substitution of organic acids with vinegar and/or acetic acid bacteria, and finally alternating aeration have been assessed. Four different combinations were applied to the “Picholine marocaine” olive variety using indigenous strains, namely Lactobacillus plantarum S1, Saccharomyces cerevisiae LD01 and Acetobacter pasteurianus KU710511 (CV01) isolated respectively from olive brine, Bouslikhen dates and Cactus. Two control tests, referring to traditional and industrial processes, were used as references. Microbial and physicochemical tests showed that the L3V combination (inoculated with A. pasteurianus KU710511 and L. plantarum S1 under the optimal growth conditions of the Acetic Acid Bacteria (AAB) strain with 6% NaCl) was found to be favorable for the growth of the Lactic Acid Bacteria (LAB) strain which plays the key role in olive fermentation. This result was confirmed by sensory evaluation, placing L3V at the top of the evaluated samples, surpassing the industrial one where a chemical debittering treatment with lye was used. In addition, alternating aeration served to increase the microbial biomass of both AAB and LAB strains along with Saccharomyces cerevisiae LD01 strain, but also to use lower concentration of NaCl and to reduce the deterioration of olives compared to the anaerobic fermentation process. Finally, a mixed starter containing the three strains was prepared in a 10-L Lab-fermenter from the L3V sample in order to improve it in subsequent studies. The prepared starter mixture could be suitable for use as a parental strain to prepare table olives for artisan and industrial application in Morocco.

Comparison of the effects of acetic acid bacteria and lactic acid bacteria on the microbial diversity of and the functional pathways in dough as revealed by high-throughput metagenomics sequencing

Knowledge of the effects of various strains of acetic acid bacteria (AAB) on sourdough remains limited. In this study, the diversity of microbial taxa in sourdoughs fermented by different starters was assessed and their functional capacity was evaluated via high-throughput metagenomics sequencing. Results showed that Erwinia (29.43%), Pantoea (45.89%), and Enterobacter (9.16%) were predominant in the blank CK treatment. Lactobacillus (91.40%), Saccharomyces (6.13%), as well as the AAB genus Acetobacter (0.61%) were the dominant microbial genera in the sourdoughs started by yeast and a strain of lactic acid bacteria (YL treatment). By contrast, the dominant genera in the sourdoughs started by yeasts and various LAB and AAB strains (YLA treatment) were Komagataeibacter (0.39%) except for the inoculated Lactobacillus (68.37%), Acetobacter (20.17%), and Saccharomyces (8.31%) species. Functional prediction of these changes in microbial community and diversity revealed that various metabolism-related pathways, including alanine, aspartate, and glutamate metabolism (21.95%), as well as amino acid biosynthesis (19.14%), were predominant in the sourdoughs started by yeast and an AAB strain (YA treatment). Moreover, arginine biosynthesis (11.65%) were the dominant pathways in the YL treatment. The fermented dough added with sourdoughs started with yeast + AAB and yeast + AAB + LAB strains had substantially higher contents (more than 48.58% in total) of essential amino acids than the dough added with sourdoughs started with yeast + LAB strain. These results demonstrated that amino acid biosynthesis has a beneficial effect on sourdoughs inoculated with an AAB strain.

Mapping the functional and strain diversity of the main microbiota involved in cocoa fermentation from Cote d’Ivoire

The variable quality of cocoa produced by farmers is still a problem in the value chain, strongly depending on microbial activities. We analyzed the variability of cocoa microbiota from all twelve producing regions in Cote d’Ivoire, and described the geographical distribution of isolated microbiota, using a mapping. Microbial species were identified by ribosomal genes sequencing, strains were typed by RFLP and their techno-functional capacities were further investigated. Results showed a restricted diversity of lactic acid bacteria (LAB) and acetic acid bacteria (AAB) with respectively 10 and 5 strains. The dominant LAB and AAB strains, notably Lactobacillus plantarum 1 A, Acetobacter pasteurianus 1 A, Acetobacter okinawensis 2 A, and Acetobacter tropicalis 3 A, were found in all regions assuming that the acid microbiota was weakly variable. In contrast, the distribution of their functional performance such as acidification capability was variable, stronger in strains from Nawa and Haut-Sassandra regions and weaker in Indenie-Djuablin and San Pedro; this distribution seemed to be random. Moreover, the study also revealed a complex yeasts population showing a wide genetic diversity with 22 species and 45 strains indicating an intraspecific heterogeneity. Strains were generally different from a region to another and the resulting yeasts microbiota was globally variable in the regions. Likewise, the functional capacities such as pectinolytic was weak in P. kudriazevii strain 2 K from Gboklè and strong in P. kudriazevii strain 2 A from Loh-Djiboua. Additionally, the quality of fermented beans was also variable in the regions. The great variation of yeasts strains in the different regions may be the main microbial factors responsible for variation of the fermented cocoa quality observed.

From waste to food: utilization of pineapple peels for vinegar production

The present study is aimed at producing vinegar from fermented pineapple byproducts (peels). The vinegar was produced after fermenting the peels of pineapple usig three selected strains of acetic acid bacteria’s. such as propionic bacterium acidipropionici, panteo agglomerans, and pantea dispersa. This article introduces a new type of acetic acid bacteria’s strains for the production of vinegar from pineapple peels. Three fermentation times (24hr, 48hr, and 72hr) and three acetic acid bacterias (propionic bacterium acidipropionici, panteo agglomerans, and pantea dispersa) were considered and arranged in a factorial experimental design. The fermentation was performed in 500 mL Erlenmeyer flasks containing 200 mL of medium at 28℃. Aeration rate, temperature, and carbon source were set as constant factors. pH, total soluble solids, total residual reducing sugar and titratable acidity were evaluated. The results showed that the vinager samples were in the range of 3.5 to 4.31, 1.3 to 2.31 obrix, 0.50 to2.47% and 3.13 to 6.15 mg/100g of pH, total soluble solids, total residual reducing sugar and titratable acidity respectively. There were significant differences (P<0.05) in the values obtained. Therefore bacterial strain and fermentation time were the most important factors affecting vinegar production. From the experimental results and interaction effects, the optimum yield of acetic acid production was found to be 6.15 g/L at fermentation time of 72h by propionic bacterium acidipropionici acetic acid bacterial strain.