Isolation and identification of termite gut symbiotic bacteria with lignocellulose-degrading potential, and their effects on the nutritive value for ruminants of some by-products

摘要

The termite gut contains different kinds of lignin and lignocellulose degrading microbes. This study was conducted to isolate and identify termite gut symbiotic bacteria with lignocellulose-degrading potential, and evaluate their effects on the chemical composition and in vitro digestibility of wheat straw and date leaves. Termite gut contents were extracted and cultured in 9 different culture media" containing lignin and lignocellulosic materials that had been prepared from water-extracted sawdust and wheat straw. Three superior bacteria capable of growing on all media, and with higher lignin peroxidase activity, were selected and subjected to molecular identification. Following this, wheat straw and date leaves were incubated with the isolated bacteria in liquid medium for 6 weeks. 16S rRNA sequence analysis showed that these isolates possessed 97, 99 and 97% similarity with Bacillus licheniformis, Ochrobactrum intermedium and Micro bacterium paludicola, respectively. The highest (P < 0.05) dry matter (DM) loss in wheat straw and date leaves was observed following treatment with B. licheniformis. In the case of wheat straw, the organic matter (OM) and neutral detergent fiber (NDF), and for date leaves OM, NDF and acid detergent lignin (ADL) contents were not influenced by the treatments (P > 0.05). The greatest and lowest (P < 0.05) ADF content of wheat straw was observed as a result of treatment with B. licheniformis and O. intermedium, respectively. However, bacterial treatments decreased (P < 0.05) ADF content of date leaves when compared to the control. Acid detergent lignin content of wheat straw was decreased (P < 0.05) by bacterial treatments in comparisons to the control. For wheat straw, the highest and lowest (P < 0.05) value of crude protein (CP) was observed in the case of M. paludicola and O. intermedium treatments, respectively. For date leaves, the CP content of the control treatment was highest (P < 0.05) among treatments. For wheat straw, bacterial treatments enhanced (P < 0.05) DM, OM and ADF digestibility when compared to the control. However, highest and lowest (P < 0.05) CP digestibility was observed using O. intermedium and M. paludicola, respectively. For date leaves, treatment with B. licheniformis significantly increased (P < 0.05) digestibility of DM, OM and NDF when compared to the others. However, CP and ADF digestibility was not different (P > 0.05) between experimental groups. Overall, the results of this study showed that the isolated bacteria partially changed the chemical composition of wheat straw and date leaves while, they improved digestibility of nutrients. These bacteria are suitable candidates for increasing nutritive value of by-products for ruminants. (C) 2016 Elsevier B.V. All rights reserved.