Enhanced Production of Bioactive Compounds from Shrimp-shell Waste in a Fed-batch Biodegradation

Abstract

Biodegradation of shrimp shell powder using Bacillus cereus EW5 strain was conducted for 96 h in a bioreactor by batch, and fed-batch strategies and the production of bioactive compounds were assayed and compared. In batch degradation, the bioreactor was filled with 1575 ml of productive medium containing 1% shrimp shell powder and 175 ml (10%, v/v) inoculum. In fed-batch strategy, culture broth was fed during 14, 42, and 70 h of degradation periods with pulse addition at a constant rate of 46.80 ml/h. The final working volume was 1.75 L for batch and 3.0 L for fed-batch operation. The cell dry weight, reducing sugar production, antioxidant activity, TLC analysis, and DNA damage inhibition activity was determined. The result of the fed-batch degradation was better compared to the batch system. The highest amount of reducing sugar (0.297±0.05 mg/ml), antioxidant activity (DPPH, 92.35%, ABTS, 98.16%), was achieved during 48 h of degradation in fed-batch mode. The highest reducing power (at A700nm = 1.55 per ml) was recorded during 96 h of degradation in fed-batch mode. Periodic addition of substrate in fed-batch system leads the higher biomass production (34.57 g/L) which was 61.77% higher than the batch (21.37 g/L) biodegradation, and consequently higher reducing sugar, and higher antioxidant activity.