Isolation and characterization of mannanase-producing bacteria for potential synbiotic application in shrimp farming

Prebiotics such as mannan-oligosaccharides (MOS) are a promising approach to improve performance and disease resistance in shrimp. To improve prebiotic utilization, we investigated the potential probiotics and their feasibility of synbiotic use in vitro. Two bacterial isolates, Man26 and Man122, were isolated from shrimp intestines and screened for mannanase, the enzyme for mannan digestion. The crude mannanase from both isolates showed optimal activities at pH 8 with optimum temperatures at 60 °C and 50 °C, respectively. The enzymes remained stable at pH 8-10 for 3 h (>70% relative activity). The thermostability range of Man26 was 20-40 °C for 20 min (>50%), while that of Man122 was 20-60 °C for 30 min (>50%). The V_max of Man122 against locust bean gum substrate was 41.15 ± 12.33 U·mg^-1, six times higher than that of Man26. The K_m of Man26 and Man122 were 18.92 ± 4.36 mg·mL^-1 and 34.53 ± 14.46 mg·mL^-1, respectively. With the addition of crude enzymes, reducing sugars of copra meal, palm kernel cake, and soybean meal were significantly increased (p < 0.05), as well as protein release. The results suggest that Man26 and Man122 could potentially be used in animal feeds and synbiotically with copra meal to improve absorption and utilization of feedstuffs.