Valorisation of aquaculture sludge into microbial protein using bioreactor with an optimised nutrients

Abstract

The present study was conducted to optimise the nutrients used for producing high nutritional biofloc in bioreactor utilising aquaculture waste. Full Factorial design (23) of independent variables such as sludge quantity (20 and 30 gL−1), carbon nitrogen ratio (15:1 and 20:1) and bioflocculant (cationic starch) doses (30 and 60 ppm) were used for optimisation. The percentage of crude protein and crude lipid in biofloc was shown to be significantly influenced by the interaction between carbon nitrogen ratio and bioflocculant dose (BC) as well as the interaction between sludge quantity, carbon nitrogen ratio, and bioflocculant dose (ABC) (p < 0.05). The floc volume of biofloc was shown to be significantly influenced by the interaction between carbon nitrogen ratio and bioflocculant dose (BC) (p < 0.05). The optimised parameters were 30 gL−1 of sludge, a carbon nitrogen ratio of 20:1, and 30 ppm of cationic starch, which resulted in a maximum CP of 27.09%, a maximum CL of 4.36%, and a maximum floc volume of 132 mL L−1. Principal component analysis (PCA) resulted in a 2 principal components (PC 1, nutritional factors which decides the nutritional composition of biofloc and PC 2, nitrification factors which are needed for biofloc formation) that explained 85% of total data variation. This study found the production of nutritive biofloc in a bioreactor using aquaculture waste with optimised nutrients.