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Shen P.,Guangxi University of Technology | Shen P.,State Key Laboratory for Conservation and Utilization of Agricultural Bioresources in the Subtropics | Han F.,Guangxi University of Technology | Su S.,Guangxi Academy of Agricultural science | And 6 more authors.
Bioresource Technology | Year: 2014

Molasses alcohol wastewater (MAW) is difficult to be bio-treated and converted into biogas. In this study, MAW mixed with pig manure (PM) in different ratios was co-digested. Biogas production, chemical oxygen demand (COD) removal and the structure of microbial communities were monitored in the process. Our results showed that under the optimal COD ratio of PM:MAW (1.0:1.5), CODremoval and biogas yield were the highest. And in fermentation tanks with different PM to MAW ratios, the structure and composition of bacterial communities varied in the early and late stage. Furthermore, the type of main bacterial operational taxonomic units (OTUs) have no differences, yet the relative abundance of OTUs varied. The current research showed that there was a good potential to the use of PM as a co-digested material to anaerobic treatment of MAW and provided references for further improving bio-treatment of MAW. © 2014 Elsevier Ltd.


Chao H.,Guangxi University | Chao H.,CAS Wuhan Institute of Virology | Wu B.,State Key Laboratory for Conservation and Utilization of Agricultural Bioresources in the Subtropics | Shen P.,Guangxi University | Shen P.,State Key Laboratory for Conservation and Utilization of Agricultural Bioresources in the Subtropics
Letters in Applied Microbiology | Year: 2015

Increase in L-serine production is of interest for industry. Here, we describe a metabolic engineering approach to increase the production of L-serine in a methylotrophic bacterium. mxaF, the gene encoding the large subunit of a methanol dehydrogenase, was cloned from Methylobacterium sp. MB200 through transposon mutagenesis. Deletion of mxaF gene prevented the strain to grow on methanol, suggesting that mxaF is involved in methanol metabolism. Overexpression of mxaF gene in the strain MB200 resulted in a fivefold increase in methanol dehydrogenase activity compared to the wild-type. Resting cell assays showed that the recombinant strain accumulated 6·6 mg ml-1 L-serine in 72 h with 30 mg ml-1 wet cells from 50 mg ml-1 glycine and 50 mg ml-1 methanol, representing a 1·5-fold increment for L-serine production in contrast to the wild-type strain. These results demonstrate that the potential for improving the production of L-serine can be achieved by overexpressing mxaF gene in methylotrophic bacteria. © 2015 The Society for Applied Microbiology.


Song Z.,Guangxi University | Song Z.,State Key Laboratory for Conservation and Utilization of Agricultural Bioresources in the Subtropics | Shen P.,Guangxi University | Shen P.,State Key Laboratory for Conservation and Utilization of Agricultural Bioresources in the Subtropics | And 10 more authors.
World Journal of Microbiology and Biotechnology | Year: 2014

Sulfur is an essential element for rhizobia, such as sulfated modified Nod factors and nitrogenase. To investigate the role of sulfur metabolism in Rhizobium-Soybean symbiosis, a transponson random insertional mutants' library was constructed and a sulfur assimilation-related gene was isolated and characterized. A mutant strain unable to utilized sulfate was screened from 11,000 random insertional mutants of Sinorhizobium fredii WGF03. Sequencing analysis showed that a sulfate assimilation-related gene (cysDN) was inserted by the Tn transponson. Mutants inactivated in cysD and cysN (SMcysDF and SMcysNF) were constructed by homologous recombination using the suicide plasmid pK18mob. The mutants SMcysDF and SMcysNF could no longer utilize sulfate as sulfur source. Phenotype analysis revealed that mutation of cysDN had multiple effects on S. fredii WGF03. Root hair deformation assay showed that the activity of Nod factors secreted by mutants SMcysDR and SMcysNR elicited minimal hair initiation only. Soybean plant tests indicated that the mutant strains delayed 1-2 days to nodulate and exhibited lower nodulation efficiency and symbiotic efficiency than the wild-type strain. The complementary strain of cysD and cysN (HcysDF and HcysNF) could restore the nodulation efficiency. © 2014 Springer Science+Business Media Dordrecht.


Song Z.,Guangxi University | Song Z.,State Key Laboratory for Conservation and Utilization of Agricultural Bioresources in the Subtropics | Ma T.,Guangxi Vocational and Technical College | Zhou Y.,Guangxi University | And 5 more authors.
Chinese Journal of Applied and Environmental Biology | Year: 2015

Sulfur is an essential element for organism, and sulfate modification of Nod factor plays a vital role in the host range and recognition efficiency. Our previous study constructed the mutants of Sinorhizobium fredii WGF03 through inactivating in cysDN by homologous single-crossover recombination. However, the cysDN mutants of S. fredii could not utilize sulfate as sulfur source, while the cysDN mutants of Sinorhizobium BR816 could grow weakly on medium with sulfate as sulfur source. This study aimed to understand the difference in activating sulfate by cysDN genes in different species of rhizobium. The cysDN mutants of S. fredii WGF03, S. fredii HN01 S. meliloti 14500 and B. japonicum 15606 were constructed by using homologous recombination: ΔcysDN-WGF03, ΔcysDN-HN01, ΔcysDN-14500 and cysNR -14500. Then the sulfur source utilization and plant tests of mutants were studied. The results showed that ΔcysDN-WGF03 and ΔcysDN-HN01 could not grow on the medium of sulfate; ΔcysDN-14500 could grow on medium with sulfate as sulfur source, but with only 30% growth of the wild type strain; there was no obvious difference in utilization of various sulfur sources by cysNR-15606 and the wild strain. Plant tests showed that the plant inoculated with ΔcysDN-WGF03, ΔcysDN-HN01 and Δ cysDN-14500 showed significantly lower average nodules number, nodules weight, plant dry weight and nitrogenase activity than wild type strains, but the complementary strains could restore the ability of using sulfate and plant symbiotic nitrogen fixation. The results indicated that cysDN genes play a key role in sulfate assimilation pathway of S. fredii WGF03, S. fredii HN01 and S. meliloti 14500, but not for B. japonicum 15606. Different species of rhizobium cysDN have different ways to activate sulfate. © 2015, Science Press. All rights reserved.

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