Carbon substrate alters growth, protein production and βglucosidase activity of a native Sarocladium spp. Isolated from mangrove sediments in Abu Dhabi

Abstract

β-glucosidase enzymes are widely used in food, fuel and pharmaceutical applications. Research efforts world-wide focus on discovering highly efficient β-Glucosidases and on identifying conditions that enhance the activity of these enzymes. A fungus identified belonging to the genus Sarocladium was isolated from mangrove sediments in Abu Dhabi and screened for β-glucosidase activity using p-Nitrophenyl β-glucopyranoside (pNG) as substrate when grown on different carbon substrates. Higher β-glucosidase activity was found when carboxymethycellulose (CMC) and lactose are used as carbon substrates (60 and 30 μM PNP.μg-1 protien.hour-1 ), whereas glucose and sucrose showed the lowest activity (~ 6 μM PNP.μg-1 protien.hour-1 ) even though the organism showed lower protein secretion rates when grown using lactose and CMC (~1.2 µg protein mg-1 biomass) compared to glucose (5 µg protein mg-1 biomass). Crude protein containing βglucosidase enzymes have an apparent optimal activity at 42°C and pH 7. The apparent Km of the crude enzyme became smaller with the inclusion of salt in the reaction (Km of 0.17 mM pNG and 0.11 mM pNG in reactions containing 0 and 0.6M NaCl respectively). Results suggest that the enzyme(s) have a higher affinity for substrate in conditions that are similar to those found in the natural environment; mainly warm temperatures and the presence of relatively high concentrations of salt. Enzymes of Sarocladium spp. maybe a solution for industrial bioprocesses that are compromised when salts accumulate in the system.

Date of Award	Dec 2016
Original language	American English
Supervisor	Lina Yousef (Supervisor)