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A lysing polysaccharide monooxygenase from Aspergillus niger effectively facilitated rumen microbial fermentation of rice straw |
Ting Li1 
, Kehui Ouyang1
, Qinghua Qiu1
, Xianghui Zhao1
, Chanjuan Liu1,*
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Jiangxi Province Key Laboratory of Animal Nutrition/Engineering Research Center of Feed Development, Jiangxi Agricultural University, Nanchang Jiangxi 330045, China |
Correspondence:
Chanjuan Liu, Tel: +86-18172826059, Fax: +86-18172826059, Email: chanjuanhx@163.com
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Received: 15 January 2024 • Revised: 11 March 2024 • Accepted: 21 April 2024 |
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| Abstract |
Objective
This study investigated the impact of Aspergillus niger lysing polysaccharide monooxygenase (AnLPMO) on in vitro rumen microbial fermentation of rice straw.
Methods
AnLPMO was heterologously expressed in Escherichia coli. Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy analyzed the surface structure of rice straw after AnLPMO treatment. Two in vitro experiments, coupled with 16S high-throughput sequencing and qRT-PCR techniques, assessed the influence of AnLPMO on rumen microbial fermentation of rice straw.
Results
AnLPMO exhibited peak activity at 40 °C and pH 6.5, with a preference for rice straw xylan hydrolysis, followed by Avicel. AnLPMO application led to the fractional removal of cellulose and hemicelluloses and a notable reduction in the levels of carbon elements and C–C groups present on the surface of rice straw. Compared to the control (no AnLPMO), supplementing AnLPMO at 1.1 U-2.0 U significantly enhanced in vitro digestibility of dry matter (IVDMD, P < 0.01), total gas production (P < 0.01), and concentrations of total volatile fatty acids (VFA, P < 0.01), acetate (P < 0.01), and ammonia-N (P < 0.01). Particularly, the 1.4 U AnLPMO group showed a 14.8% increase in IVDMD. In the second experiment, compared to deactivated AnLPMO (1.4 U), supplementing bioactive AnLPMO at 1.4 U increased IVDMD (P = 0.01), total gas production (P = 0.04), and concentrations of total VFA (P < 0.01), propionate (P < 0.01), and ammonia-N (P < 0.01), with a limited 9.6% increase in IVDMD. Supplementing AnLPMO stimulated the growth of ruminal bacterial taxa facilitating fiber degradation, including Proteobacteria, Spirochaetes, Succinivibrio, Rikenellaceae_RC9_Gut_Group, Prevotelaceae_UCG-003, Desulfovibrio, Fibrobacter succinogenes, Ruminococcus albus, R. flavefaciens, Prevotella bryantii, P. ruminicola, and Treponema bryantii.
Conclusion
These findings highlight AnLPMO's potential as a feed additive for improving rice straw utilization in ruminant production.
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| Keywords:
In vitro Rumen Fermentation; Lysing Polysaccharide Monooxygenase; Microbial Community; Rice Straw; Surface Structure |
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