Abstract

The present study is concerned with the selection of new economical media based on agricultural and marine-processing by-products for the production of alkaline proteases by Bacillus licheniformis NH1. Powders from different fish species were prepared and then tested as growth media at a concentration of 10 g/l for proteases production by NH1 strain. Powder prepared from whole Sardinelle was found to be the best substrate for the production of the alkaline protease. The NH1 strain exhibited a slightly greater protease production (2927 U/ml) in medium containing only whole Sardinelle powder than that obtained in control medium (2800 U/ml). Proteases were produced even when strain NH1 was cultivated in medium containing only powder prepared from combined heads and viscera Sardinelle (CHVSP), about 2117 U/ml. Protease production was also carried out in media containing hulled grain of wheat, a by-product of semolina factories, as carbon source. Maximum activity (2517 U/ml) was achieved when the strain was grown in medium containing hulled grain of wheat (10 g/l), casein peptone (2 g/l), K₂HPO₄(0.5 g/l) and KH₂PO₄ (0.5 g/l). Moreover, protease production was considerably enhanced when the strain was grown in medium containing both hulled grain of wheat and CHVSP as carbon and nitrogen sources, respectively, (4771 U/ml). The study shows that hulled grain of wheat and powders from fishery by-products could be utilized as bacterial substrates for the production of alkaline proteases by B. licheniformis NH1.

Key words: Fish powder, hulled grain of wheat, heads and viscera, alkaline protease, Bacillus licheniformis NH1.

Abbreviation

CHVSP, Combined heads and viscera Sardinelle powder; LB, Luria-Bertani; SDS-PAGE, sodium dodecyl sulphate-polyacrylamide gel electrophoresis;MSP, meat Sardinelle powder; WSP, whole Sardinelle powder