Abstract

α-Amylases (EC 3.2.1.1; 1,4-α-D-glucanglucanohydrolase) are enzymes that are widely studied and used in industries. Amylase production is affected by substrate and heavy metals. The effects of various carbon and nitrogen sources and heavy metals concentrations on α-amylase production by submerged fermentation (smF) from lactic acid bacteria strains were investigated. Amylase producing bacteria were isolated from fermented starchy samples collected from local producers in Aba, Abia state thereafter screened for amylase activity on starch agar medium.  Effect of carbon and nitrogen sources on amylase production was carried out. The effects of nutrient conditions on the amylase production were found to be significant (P˂ 0.05). Cassava flour (1%w/v) was found to be favorable carbon source for   α-amylase production by all the strain with the amylase activity of 1.16 U/ml for Lactobacillus plantarumFMO2, 0.80 U/ml for Lactobacillus plantarumZ2 and 0.92 U/ml for Lactobacillus pentosus BSR3 compared to the control (starch) 0.47U/ml. Of the nitrogen sources tested, peptone (1.5w/v) led to the production of maximum amount of α-amylase of 1.11U/ml, 0.84U/ml and 0.96 U/ml for Lactobacillus plantarumFMO2, Lactobacillus plantarumZ2 and Lactobacillus pentosus BSR3 respectively compared to the control (yeast) 0.42U/m. The effects of different heavy metals on the production of α-amylase from Lactobacillus plantarumFMO2 as the  was activated by Ca²⁺, strongly inhibited by Cu²⁺ but less affected by Mg²⁺ and  Fe²⁺at 0.1w/v concentrations. The application of cheaper and readily available agro-industrial substrates such as cassava flour as carbon source and peptone as nitrogen source with Ca²⁺ may be considered a better nutrient additive for optimum growth of the bacteria and amylase production.