Effect of Lactobacillus rhamnosus microencapsulated by alginate/chitosan in two ways, ionic gelation and internal emulsification on growth and nutrition performance and digestive enzymes activity of rainbow trout (Oncorhynchus mykiss)

Technology of probiotics encapsulation is one of the newest methods to increase the stability of probiotics. In the current study, the effects of encapsulation of Lactobacillus rhamnosus by alginate/chitosan in two ways, ionic gelation and internal emulsification on nutrition and growth performance and digestive enzymes activity in rainbow trout were evaluated. An experiment was designed with five treatments each with three replicates. 600 juvenile average (±SD) initial weight of 25.53±.82 g were assigned to 4 treatments (each with 3 replications). Fish in T1 and T2 received Lactobacillus rhamnosus encapsulated by Ionic gelation and internal emulsification respectively, T3 were fed with alginate/chitosan enriched free probiotic diet, T4 received bacteria without any encapsulation and control group. Fish were fed with experimental diets for 60 days and the study continued for a further 15 days with basic diet in all treatments. Fish were sampled on days 30, 60 and 75 and food conversion ratio, protein efficiency ratio, specific growth rate, condition factor, weight gain percentage and digestive enzymes activity (lipase, protease, trypsin and chymotrypsin) were compared among the treatments. The lowest food conversion ratio (0.93±0.03) at day 30 was seen in T2 which was significantly different from control treatment (p<0.05). Protein efficiency ratio values at days 30, 60 and condition factor at day 60 were higher in T1 and T2, that this increase was significant in T2 than control group (p<0.05). Also, the measurement of digestive enzymes showed the high level of lipase and protease in microencapsulated treatments compared to other treatments.It can be concluded that the microencapsulation of Lactobacillus rhamnosus by internal emulsification with alginate/chitosan has significant effects on some of nutrition and growth performance and digestive enzymes activity in rainbow trout and the use of this method to improve the performance of the probiotic in rainbow trout is recommended.