Characterization of Thermotolerant Acetic Acid Bacteria Isolated from Various Plant Beverages in Thailand

 Background and objective: Thermotolerant acetic acid bacteria are more resistant to high temperatures than that other bacteria are. This difference includes 5-10ºC, which decreases high costs of cooling systems needed for the growth of these bacteria while preserving their high productivity. In this study, effective thermotolerant acetic acid bacteria isolated from various fermented plant beverages were characterized for their ability to produce acetic acid and their characteristics were investigated.Materials and methods: Various thermotolerant acetic acid bacteria isolated from fermented plant beverages samples were investigated for their ability to produce acetic acid at high temperature. Two isolates of Acetobacter pasteurianus were selected and their growth and acetic acid production ability were assessed under various conditions. Furthermore, capsular polysaccharides of these strains were extracted and characterized using gas-liquid chromatography and Fourier-transform infrared spectroscopy.Results and conclusion: In this study, Acetobacter pasteurianus and Acetobacter tropicalis were dominant thermotolerant acetic acid bacteria in the fermented plant beverage. Two isolates of Acetobacter pasteurianus, Fermented Plant Beverages 2-3 and 2-16, produced acetic acid effectively at 39°C, compared to that Acetobacter pasteurianus SKU1108 did as a superior control for thermotolerant acetic acid bacteria. Fermented Plant Beverage 2-3 was able to completely oxidize 5% v v-1 ethanol to acetic acid at 39°C, while a long lag time was observed at 6% ethanol. However, production of acetic acid was still up to 4% w v-1. Moreover, this isolate exhibited excellent resistance to acetic acid at high temperatures, compared to 2 other strains in liquid and solid media. However capsular polysaccharides isolated from the 3 strains included glucose, rhamnose and galactose. Fourier-transform infrared spectroscopy spectra of capsular polysaccharides from Fermented Plant Beverage 2-3 at 1740 cm-1 identified a clearly different O-acetyl ester. This might be attributed to different O-acetyl ester contents of the capsular polysaccharides and also to resistance to acetic acid and high temperature.Conflict of interest: The authors declare no conflict of interest

Bioconversion of biodiesel-derived crude glycerol to 1,3-dihydroxyacetone by a potential acetic acid bacteria

Acetic acid bacteria (AAB) isolated from natural resources and fermented plant beverages were screened to produce 1,3-dihydroxyacetone (DHA) from non-detoxified crude glycerol. Among them, the isolate NKC115 was identified as Gluconobacter frateurii and produced the highest amounts of DHA. Subsequently, the effects of growth-medium conditions (initial pH, crude glycerol concentration and nitrogen sources) on growth and DHA-production capability were examined. The results showed that the crude glycerol concentration increase to above 100 g/L suppressed growth and DHA production. The highest amount of DHA obtained was 27.50 g/L, from an initial crude glycerol concentration of 100 g/L. Meanwhile, an initial pH of 5.5-7.5 in the YPGc medium did not significantly affect the bacterial growth and DHA production. The optimal nitrogen source was peptone, with DHA production at 34.70 g/L. Furthermore, overexpression of the nhaK2 gene encoding for the Na+(K+)/H+ antiporter from Acetobactor tropicalis SKU1100 in G. frateurii NKC115 improved growth and increased the accumulation of DHA (37.25 g/L) from an initial crude glycerol concentration of 20%. These results indicated that the expression of this antiporter might maintain an optimal intracellular pH and concentration of Na+ or K+, leading to the cells’ ability to tolerate high concentrations of crude glycerol

Valorization of Aquatic Weed and Agricultural Residues for Innovative Biopolymer Production and Their Biodegradation

From MDPI via Jisc Publications RouterHistory: accepted 2021-08-17, pub-electronic 2021-08-24Publication status: PublishedFunder: National Research Council of Thailand (NRCT); Grant(s): National Research Council of Thailand (NRCT)In this work, water hyacinths, bagasse and rice straw were valorized to produce an innovative biopolymer. Serial steps of extraction, bleaching and conversion of cellulose to be carboxymethylcellulose (CMC) as well as the last steps of blending and molding were performed. The CMC was mixed with tapioca starch solution by a ratio of 9:18, and a plastic sizer of glycerol was varied at 2%, 4% and 6% by volume. In addition, bioplastic sheets were further determined in their properties and biodegradation. The results revealed that bioplastics with 6% glycerol showed a high moisture content of 23% and water solubility was increased by about 47.94% over 24 h. The effect of temperature on bioplastic stability was found in the ranges of 146.28–169.25 °C. Furthermore, bioplastic sheets with 2% glycerol could maintain their shape. Moreover, for texture analysis, the highest elastic texture in the range of 33.74–38.68% with 6% glycerol was used. Moreover, bioplastics were then tested for their biodegradation by landfill method. Under natural conditions, they degraded at about 10.75% by weight over 24 h after burying in 10 cm soil depth. After 144 h, bioplastics were completely decomposed. Successfully, the application of water, weed and agricultural wastes as raw materials to produce innovative bioplastic showed maximum benefits for an environmentally friendly product, which could also be a guideline for an alternative to replace synthetic plastics derived from petroleum

Batch Fermentation of Salt-Acclimatizing Microalga for Omega-3 Docosahexaenoic Acid Production Using Biodiesel-Derived Crude Glycerol Waste as a Low-Cost Substrate

Biodiesel produced from waste cooking oil (WCO) is on the rise and inevitably leads to issues in managing glycerol waste. Due to the presence of colour, odour and other minor compounds, the refining costs for this type of glycerol are higher and uneconomical. The potential of biodiesel-derived glycerol waste (BDGW) obtained from WCO to produce the highly added product of docosahexaenoic acid (DHA), also known as omega-3 polyunsaturated fatty acid, via the marine microalga of Schizochytrium limacinum ATCC MYA-1381 under aerobic batch fermentation was investigated. Cell growth, as well as DHA production, were performed under various operating conditions, including aeration rates and BDGW concentrations. The effect of the substrate type on cell growth and DHA yield was evaluated. The optimum operating condition was obtained when the air flow of a 0.25 vvm and 50 g/L of the glycerol concentration was fed into the fermenter and maximum cell dry weight (11.40 g/L) and DHA yield (665.52 mg/g) were achieved. However, cell growth and DHA yield were not significantly different when S. limacinum was grown using various carbon sources. Successfully, it clearly demonstrates that the BDGW can be used as a cheap carbon source for DHA production via marine microalgae using aerobic batch fermentation