Abstract:
Amylases are important enzymes commonly used for the hydrolysis of starch to generate hydrolysates useful for different industrial applications. This study was aimed at isolating amylase producing fungal species from decomposed wastes and spoiled foods using solid state fermentation. The isolated fungal species were screened experimentally using the starch hydrolysis test and identified based on cultural and microscopic characteristics. Amylase activity was determined using the dinitrosalicylic acid (DNS) method. Optimizations of fermentation parameters were carried out for maximum production of amylase by fungal isolates using the one-factor-at a time method. Data were analyzed using analysis of variance (ANOVA) and differences between mean values were considered statistically significant at P≤0.05. The results indicated that a total of twelve fungal isolates were obtained from four investigated samples. Of these, five isolates designated as AWI01 (6.4 cm), AWI02 (7.9 cm), KWI02 (5.8 cm), SBI03 (6.5 cm) and SPI01 (6.3 cm) showed very large zone of hydrolysis on starch agar plate and used in SSF containing three levels of substrates (100% Corn cob, 100%Potato peel and 50% Corn cob +50% Potato peel). Among the five isolates, isolate AWI02 was found the best amylase producer (0.397 U/ml). As a result, it was selected for optimization studies. Similarly, among the three substrates, 100%PP showed highest amylase production and hence it was chosen for optimization processes. Morphological study of AWI02 indicated that the isolate belonged to the genus Aspergillus. The optimal incubation period, moisture content, temperature and initial pH for amylase production by AWI02 were found to be 5 days (0.592 U/ml), 15ml (0.449 U/ml), 30oC (0.475 U/ml) and 6.0 (0.585 U/ml), respectively. Soluble starch and yeast extract were the best carbon and nitrogen sources for amylase production, respectively. The amylase produced by isolate AW102 was optimally active at 45oC and a pH of 6.0. With regards to the concentration of substrate, amylase showed highest activity at 1% starch concentration. Generally, the findings of the present study suggested that AWI02 (Aspergillus sp.) could serve as a very important candidate for large scale production of amylase using potato peel as a source of cheap substrate