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A lysing polysaccharide monooxygenase from Aspergillus niger effectively facilitated rumen microbial fermentation of
Ting Li1, Kehui OuYang1, Qinghua Qiu1
1Jiangxi Province Key Laboratory of Animal Nutrition/Engineering Research Center of Feed Development, Jiangxi Agricultural University, Nanchang Jiangxi 330045, China.
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 highthroughput sequencing and quantitative real-time polymerase chain reaction 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 to 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.
Insights
Aspergillus niger lysing polysaccharide monooxygenase (AnLPMO) enhances rice straw digestibility and volatile fatty acid production in ruminants. This enzyme shows potential as a feed additive to improve ruminant production by boosting microbial fermentation of fibrous feed.
Area of Science:
- Biotechnology
- Animal Science
- Microbiology
Background:
- Rice straw is a major agricultural byproduct with significant potential for ruminant feed.
- Its low digestibility due to complex lignocellulosic structure limits its utilization.
- Enzymatic pre-treatment offers a promising strategy to enhance the nutritional value of fibrous feedstuffs.
Purpose of the Study:
- To investigate the efficacy of Aspergillus niger lysing polysaccharide monooxygenase (AnLPMO) in improving in vitro rumen microbial fermentation of rice straw.
- To analyze the impact of AnLPMO on the physical and chemical properties of rice straw.
- To assess the effects of AnLPMO on ruminal fermentation parameters and microbial community composition.
Main Methods:
- Heterologous expression and characterization of AnLPMO.
- Surface analysis of rice straw using Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy.
- In vitro rumen fermentation assays with 16S high-throughput sequencing and qPCR to evaluate digestibility, gas production, volatile fatty acids, and microbial populations.
Main Results:
- AnLPMO effectively hydrolyzed rice straw xylan and Avicel, reducing surface carbon content.
- Supplementation with AnLPMO significantly increased in vitro dry matter digestibility (IVDMD), total gas production, and volatile fatty acid (VFA) concentrations.
- AnLPMO stimulated the growth of key fiber-degrading ruminal bacteria, enhancing overall fermentation efficiency.
Conclusions:
- AnLPMO demonstrates significant potential to improve the nutritional value and digestibility of rice straw for ruminants.
- The enzyme's ability to modify rice straw structure and promote beneficial microbial growth supports its application as a feed additive.
- Further research can explore AnLPMO's application in vivo to optimize ruminant production systems.
