Isolation and characterization of yeast for glucoamylase production
Loading...
Date
2007
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
CCSHAU
Abstract
Glucoamylase is the major enzyme required for complete hydrolysis of starch to
glucose, which can be used as carbon source in fermentation for ethanol production. It
also has large application in food industries and distilleries. The demand for
glucoamylase has increased many folds due to utilization of non-conventional substrates
(starchy raw material) for industrial ethanol production. The screening of organism that
produce large amount of enzyme has been a major area to improve the efficiency of
starch processing. Nineteen starch assimilating yeasts were isolated from various sources
(ripened fruits, spoiled vegetables, bakery samples, soil, unfermented wort and honey
etc). Screening of glucoamylase producing yeast was done by starch plate iodine test and
estimating glucoamylase activity. NY-19 and NY-3 isolated from unfermented wort and
banana produced 9.2 and 9.6 IU/ml glucoamylase and were finally selected along with
Saccharomycopsis fibuligera MTCC-3816 (reference strain). The reaction of 400 ml of
cultural filtrate with 1% starch substrate at pH of 4.8 and 30oC temperature for one
minute was found optimum for enzyme assay. At optima temperature (30oC), pH (5.0)
glucoamylase production by NY-19, NY-3 and MTCC-3816 were 14.40, 13.00 and
15.97 IU/ml, respectively after 48 h of incubation under shake condition. Starch (3%),
yeast extract (1%) and peptone (2%) were best carbon and nitrogen source respectively.
However MTCC-3816 gave higher activity at 2% starch. The glucoamylase produced
from NY-19 was partially purified to 10 fold with specific activity of 43.33 IU/mg of
protein using (NH4)2SO4 fractionation. The partially purified enzyme has optimum
temperature of 500C and pH 4.8 and was thermostable up to 400C for 8 h. 87%
saccharification of rice flour slurry (30%) attained under optimum conditions of
temperature (500C) and pH (4.5) in 2 h using Palkozyme HT Plus (liquefying enzyme)
and glucoamylase preparation form NY-19. On the basis of morphological and
biochemical characteristics isolate NY-19 was identified as Endomycopsis sp.
Description
Keywords
Yeast, Glucoamylase, Starch, Rice flour, Liquefaction, Saccharification