Isolation and Characterization of Cellulolytic Marine Bacteria for Litopenaeus Vannamei Aquaculture Using Sugarcane Bagasse as Carbon Source

Abstract

Background: In aquaculture system, it is essential to adjust the inherent disadvantage of C/N ratio by adding a lot of additional carbon sources, such as sugarcane molasses, organic acids, and organic acid salts, which will greatly increase the cost of shrimp aquaculture. Herein, we aimed to isolate cellulolytic marine bacteria to hydrolyze sugarcane bagasse (SB) for reducing the cost of addition of external carbon sources in industrial Litopenaeus vannamei aquaculture.Results: A total of 97 cellulolytic marine bacterial strains belonged to 6 genera were isolated from 2,585 indigenous bacteria, indicating that seagrass bed can be used as an important place for screening the cellulolytic bacteria. The hydrolysis capacity (HC) of 58 cellulolytic marine bacterial strains was ranged from 1.1–4.0. MW-M5 displayed the largest HC value, followed by MW-M10 and MW-M14. The cellulase contents of 30 strains were more than 3 U/g in the supernatant of fermentation broth after 24 h, which was significantly higher than that of commercial cellulose. 26 cellulolytic marine bacteria with HC greater than 2 were safe for L. vannamei. MW-M19 with the lowest multiple antibiotic resistance index, 0.1, had a highest SB enzyme activity, 4.14 U/mL. The SB decomposition rates of CFW-C18 and MW-M15 were up to about 63.81% and 48.57% after fifteen days, respectively. Conclusions: These results provide valuable information for further construction of a shrimp aquaculture system based on low-cost external carbon sources using cellulolytic bacteria, and even for other biotechnological applications.