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20131
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Subject: Microbiology × Author: Sandeep Kaur × Type: Thesis × Thesis Type: M.Sc ×
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    PRODUCTION OF RICE VINEGAR AND DNA FINGERPRINTING OF FERMENTING MICROORGANISMS
    (2013) Sandeep Kaur
    The present study envisaged to isolate ethanol producing yeast and acetic acid producing bacteria from natural sources for vinegar production from two rice varieties, Basmati (PUSA 1121) and parmal (PR 116). The saccharification of rice starch was optimised through response surface methodology. Using crude enzyme at 60°C, maximum sugars were obtained in the wort of 20% substrate i.e. 110 and 95 mg/ml glucose from rice varieties PUSA 1121 and PR 116 respectively. With commercial enzyme too, maximum sugars were obtained with 20% substrate i.e. 172 mg/ml glucose with PUSA 1121 at 54.5°C and 133 mg/ml glucose with PR 116 at 60°C, hence giving saccharification efficiency of 95% and 90% respectively. PUSA 1121 was validated to have saccharified optimally at 20% substrate, pH 5.3, temperature 54°C and 30 IU/g alpha amylase and 50 IU/g glucoamylase. Similarly PR 116 was best saccharified at 20% substrate, pH 5.6, temperature 60°C and 30 IU each of alpha amylase and glucoamylase. Out of 20 yeast isolates screened, the isolate Y-4 gave maximum 79.25% fermentation efficiency, hence was used to produce ethanol by two techniques, separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). In SHF, Y-4 produced 7.64% (w/v) and 6.82% (w/v) ethanol from PUSA 1121 and PR 116 worts having initial sugar concentration of 17.2% and 14% respectively. However, SSF led to decreased ethanol production i.e. 5.88% (w/v) from parmal rice and 6.82% (w/v) from basmati rice with the same initial sugar levels in the wort. Characteristically Y-4 utilized fructose, dextrose, galactose and mannose, reproduced by lateral budding, sensitive to cycloheximidine, lacked lipolytic activity and unable to produce starch and was identified as Issatchenkia orientalis F701 (Pichia kudriavzeii). It stands deposited in GenBank with accession no. JX537791. On the other hand, standard culture of Acetobacter acetii NRRL 746 from the Dept. of Microbiology, P.A.U, Ludhiana was used for acetic acid production from ethanol. An 8% ethanol wort produced 6.51% (w/v) volatile acids in PUSA 1121 and 5.08% (w/v) volatile acids in PR 116 in the lab studies. In the scale up production of vinegar to 5 litre, the volatile acidity levels were 5.10 and 4.86% (w/v) for respective rice varieties. The sensory evaluation of vinegar samples scored 7.59 and 8.27 points on 10 point scale for basmati and parmal varieties of rice respectively. Both types of rice vinegar were analyzed to have elements such as Fe, Na, K, Mg, Ca, Zn within acceptable limits according to Codex Alimentarius (2000).