Isolation and Characterization of Mannanase-Producing Bacteria for Potential Synbiotic Application in Shrimp Farming.

Abstract

Simple SummaryMannooligosaccharides (MOS) can promote growth and immunity in aquatic animals. Although most commercial MOS are derived from yeast, the use of MOS from copra meal, a waste product of the coconut industry, is of interest. MOS from copra meal, when given as a dietary supplement to shrimp, could help improve resistance to pathogenic Vibrio and could also act as an immunostimulant. Our objective was to identify bacterial isolates that could be used as probiotics for shrimp and together with MOS as synbiotics to synergistically improve shrimp performance and feed utilization. In this study, two bacterial candidates, Man26 and Man122, were isolated from shrimp intestines and screened for mannanase, the enzyme for mannan digestion. The crude enzymes were evaluated for their biological properties and potential application in the digestion of feedstuffs in vitro. Both strains were able to produce and secrete mannanase to digest MOS and other mannan-rich materials and could tolerate a wide pH range. The addition of crude enzymes significantly increased the reducing sugars of copra meal, palm kernel cake, and soybean meal (p < 0.05) as well as protein release. The synergistic effect of our bacteria and MOS on shrimp growth performance will be further explored in the field.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 Vmax of Man122 against locust bean gum substrate was 41.15 ± 12.33 U·mg−1, six times higher than that of Man26. The Km 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.