Evaluation of Acetic Acid Bacteria for Production of Organic Vinegar from Chepa guti, a waste by product of rice based alcoholic fermentation
Chepa guti, a byproduct of the Xaj-brewing process is the lees left behind after the liquid is separated from the fermented product. The technological advance in the field of rice brewing is expected to witness an upsurge in brewing plant and an increase generation of this byproduct. Chepa guti is specifically seen to retain starch and fermentable sugars which can be used to produce down stream products like acetic acid. Chepa guti collected from different localities were used as a source for isolation of acetic acid bacteria. Three isolates that matched acetobacter species on biochemical level were further characterized at the molecular level through 16SrDNA gene sequencing and identified as Acetobacter indonesiensis, Acetobacter spp. and Acetobacter tropicalis. The collected chepa guti was initially characterized at the biochemical level and subjected to hydrolysis with commercial alpha-amylase at different concentration for generating maximum amount of reducing sugar. The aamylase at 0.3 per cent concentration in 1:1.5 substrate dilution (substrate : water) along with fungal culture Amylomyces rouxii ABT82 (NCBI KP790015) at 48 hours of incubation time produced maximum reducing sugars (73.41 mg 100mL-1). Simultaneous saccharification and fermentation using the yeast isolate Saccharomyces cerevisiae ADJ 5 (NCBI KX904349) produced 8.19 % ethanol. This substrate was used to produce acetic acid by inoculating pure culture of isolated acetic acid bacteria viz., Acetobacter indonesiensis , Acetobacter spp , Acetobacter tropicalis along with a control inoculated with reference strain Acetobacter aceti ATCC 15973 and treatment combination. Acetic produced by the pure culture of Acetobacter tropicalis was significantly higher in terms of acetic acid content of (9.08 %). It had pH (2.68), residual alcohol of (0.52 %), TSS of (0.91 ˚Brix), residual reducing sugar of (0.25 mg 100 mL-1) and protein content of (68.09 μg 100 mL-1). The LC-MS analysis of the produced acetic acid showed the presence of compounds like O-Phosphoserine, 2',3'-Dideoxyadenosine, Phenylalanine, 2-(4-Hydroxyphenyl) propionic acid, Creatine, N-Tigloylglycine, S-Sulforaphene, Triethyl phosphate, Metazachlor-OXA, Histidinol, Indole, Indoline, L-verbenone, Indole-3-carbinol, DL-Pipercolic acid, 1-Aminocyclopropane carboxylic acid. The Acetobacter tropicalis isolate was used in the scale up process where acetic acid content of (11.26 %) was achieved by increasing the inoculum size. The study reveals the potential of native acetic acid bacteria and development of a technology to produce organic acetic acid from bio-waste. The study was successful in isolating and identifying native acetic acid bacteria in Chepa guti and also was able to standardize the production of vinegar from the biowaste.