The eri silkworm, Samia ricini, is associated with symbiotic bacteria believed to be playing several physiological functions to the host. The larvae of S. ricini were subjected to isolation of gut bacteria using culture-dependent 16S rRNA gene amplification and sequencing; and qualitative and quantitative enzymatic assays. The results of qualitative cellulolytic assays indicated that 58% of the screened gut bacterial isolates had cellulolytic activity. The cellulolytic bacterial isolates belonged to Bacillus sp. (88%), Pseudomonas sp. (8%) and Enterococcus sp. (4%). Quantitative assays indicated that the highest β-glucosidase (13.42 U/mg), endoglucanase (3.60 U/mg) and exoglucanase (2.60 U/mg) activity were in isolates ERI011, ERI009 and ERI097, respectively. Our results further indicate that significant activities of endogenous cellulases are present in the gut fluids of S. ricini. However, a comparative analysis of the cellulolytic activity showed that the endoglucanase activity of bacterial origin was 13 and 18-fold higher in the foregut and midgut, respectively, than that in gut fluids. Similarly, the β-glucosidase activity was 20 and ninefold higher compared with gut fluids from the same compartments. The higher cellulolytic activity of bacterial origin compared with that of insect origin suggests that more cellulose digestion may be aided by cellulases of bacterial origin. These cellulolytic gut bacterial isolates may be good sources for profiling novel genes and biomolecules for biotechnological application.

蚕（Samia ricini）与共生细菌有关，据信它们对宿主发挥着几种生理功能。使用依赖于培养物的16S rRNA基因扩增和测序分离蓖麻链球菌幼虫的肠道细菌。以及定性和定量酶促测定。定性纤维素分解测定的结果表明，所筛选的肠道细菌分离物的58％具有纤维素分解活性。纤维素分解菌属于芽孢杆菌。（88％），假单胞菌属。（8％）和Enterococcus sp。（4％）。定量分析表明，最高的β葡糖苷酶（13.42 U / mg），内切葡聚糖酶（3.60 U / mg）和外切葡聚糖酶（2.60 U / mg）的活性分别在菌株ERI011，ERI009和ERI097中。我们的结果进一步表明，内源纤维素酶的显着活性存在于蓖麻链球菌的肠液中。然而，对纤维素分解活性的比较分析表明，细菌来源的内切葡聚糖酶活性在前肠和中肠中分别比在肠液中高13到18倍。同样，β-葡萄糖苷酶与来自相同隔室的肠液相比，其活性分别高20倍和9倍。与昆虫来源相比，细菌来源的纤维素分解活性更高，这表明细菌来源的纤维素酶可以帮助更多的纤维素消化。这些纤维素分解肠细菌分离物可能是分析新基因和生物分子以供生物技术应用的良好来源。