Screening Of A Acid-Stable α-Amylase Producing Strain And Study On Its Fermentation Products

A strain producing acid-stable α—amylase was isolated from vinegar fermentation medium of a condiment factory. It was identified as Candida aquatica and was called ASA-1.Through solid fermentation, we knew that the enzyme activity of ASA-1 was 30.6U/g. After some complex mutagenetic treatment on strains ASA-1, a stable mutant strain with high yield of acid-stable α—amylase was obtained. First, using a dosage with a death rate of 80%. the strain ASA-1 was treated by UV and we selected some mutant strains. Second, using a dosage with a death rate of 80%, the mutant strains were treated by DES-UV, we obtained a mutant called ASA-UD86. which has a high-out acid-stable α—amylase. The enzyme activity of ASA-UD86 rose up to 146U/g as compared with 30.6U/g of the original strain.The solid-state fermentation for production of acid-stable α—amylase was studied in wheat bran medium. The proportion of bran to bean cake is 1:0.5; the proportion of solid to water is 1:1.2. Initial pH is natural and incubation tern is 30'C.The precipitate of the soaked suspension was dissolved into 0.1M acetate buffer(pH4.0) containing 0.5% NaCl. The result of acrylamide gel electrophoresis showed that the crude enzyme included three isoenzymes.