Evaluation of Acetic Acid Bacteria for Production of Organic Vinegar from Chepa guti, a waste by product of rice based alcoholic fermentation
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Date
2018
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Abstract
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.