Physicochemical and kinetic properties of a high salt tolerant Aspergillus flavus glucoamylase

Production of Glucoamylase from Novel Strain of Alternaria Alternata under Solid State Fermentation

Glucoamylase has an essential role as biocatalyst in various important industries of Pakistan. It is synthesized by using various fungal and bacterial strains, and different ecocultural conditions are applied under solid substrate fermentation method (SSF) to get the highest yield of glucoamylase. Alternaria alternata is an important fungus that can grow on industrial raw material like wheat bran, dried potato powder, tea leaves, rice husk, and sugar cane peel which are used as substrate. Among all, dried potato powder (10g) proved the best fermentation media for growth of fungal strain as well as maximum glucoamylase producer. Moreover, several chemical and physical states were also explored through solid substrate fermentation technique on glucoamylase yield. The highest glucoamylase production was recorded after 72 hours incubation in incubation chamber with 10g raw substrate, 1ml inoculum spore solution, 30°C temperature, and 5 pH. Further, phosphate buffer (5 pH) as moistening agent, 5% starch concentration and media additive as nitrogen (yeast extract), and carbon source (maltose) were screened for maximum glucoamylase titer ( $17.3\pm 0.05$ a°U/ml/min) and the highest specific activity (39.2U/mg). These cultural conditions were most appropriate for growth of A. alternata on solid media and production of highest glucoamylase under solid state fermentation procedure that could be utilized for commercial synthesis of glucoamylase.

Biochemical characterization of a surfactant-stable keratinase purified from Proteus vulgaris EMB-14 grown on low-cost feather meal

OBJECTIVES

The bioaccumulation of keratinous wastes from poultry and dairy industries poses a danger of instability to the biosphere due to resistance to common proteolysis and as such, microbial- and enzyme-mediated biodegradation are discussed.

RESULTS

In submerged fermentation medium, Proteus vulgaris EMB-14 utilized and efficiently degraded feather, fur and scales by secreting exogenous keratinase. The keratinase was purified 14-fold as a monomeric 49 kDa by DEAE-Sephadex A-50 anion exchange and Sephadex G-100 size-exclusion chromatography. It exhibited optimum activity at pH 9.0 and 60 °C and was alkaline thermostable (pH 7.0-11.0), retaining 87% of initial activity after 1 h pre-incubation at 60 °C. The K_m and V_max of the keratinase with keratin azure were respectively 0.283 mg/mL and 0.241 U/mL/min. Activity of P. vulgaris keratinase was stimulated by Ca²⁺, Mg²⁺, Zn²⁺, Na⁺ and maintained in the presence of some denaturing agents, except β-mercaptoethanol while Cu²⁺ and Pb²⁺ showed competitive and non-competitive inhibition with K_i 6.5 mM and 17.5 mM, respectively.

CONCLUSION

This purified P. vulgaris keratinase could be surveyed for the biotechnological transformation of bioorganic keratinous wastes into valuable products such as soluble peptides, cosmetics and biodegradable thermoplastics.