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Raw Starch-Digesting Amylase from Saccharomycopsis
fibuligera 2074 Isolated from Bubod Starter

Jennifer Pena Fronteras* and Lani Lee R. Bullo

Department of Food Science and Chemistry
College of Science and Mathematics,
University of the Philippines Mindanao, Tugbok District
Davao City, Philippines 8022

*corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

ABSTRACT
Eight microbial isolates from bubod starter purchased from the Philippine National Collection of Microorganisms displayed amylolytic activity on raw sago starch indicating that they are possible sources of raw starch-digesting amylases (RSDA). Saccharomycopsis fibuligera 2074 showed the highest activity followed by Saccharomycopsis bubodii 2066 as determined through Dinitrosalicylic Acid Method. For Saccharomycopsis fibuligera 2074, maximum amylase production was obtained from 36-hour culture using 1% raw sago starch as carbon source under static incubation. The enzyme was purified via two-step purification protocol involving ammonium sulfate precipitation and diethylaminoethyl cellulose chromatography to give a specific activity of 180.49 U/mg and 2.57 purification fold. Further characterization of the enzyme showed that the amylase activity was optimum at pH 6 and temperature of 40°C. Although the enzyme was inhibited by Cu2+, Zn2+, and Al3+, it was activated by Ca2+, Fe3+, Ba2+, phenylmethylsulfonyl fluoride and ethylenediaminetetraacetic acid. On the other hand, iodoacetic acid, K+, Cd2+, and Mg2+, showed no significant effect on the amylase activity. Saccharomycopsis fibuligera 2074 showed to be a promising source of RSDA to allow the direct and less costly conversion of raw sago starch to glucose.

INTRODUCTION
In the Philippines particularly in the Mindanao region, sago palm (Metroxylon sagu Rottb.) is an abundant indigenous source of raw starch (Flores 2008). However, utilization of sago starch in food is yet very limited as Filipinos prefer rice or corn as staple. An alternative promising use of sago starch is for the production of glucose which in turn, can be converted to many high-value products such as ethanol and lactic acid. However, due to the resiliency of starch structure, it needs to undergo pre-treatment steps consisting of gelatinization, liquefaction and saccharification prior to its complete hydrolysis to glucose. These processes require high energy input as they entail heating of starch at elevated temperatures for relatively long time. This renders production of starch hydrolysates very expensive (Mamo and Gessesse 1999; Goyal et al. 2005). . . . read more

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