Effects of ferulic acid esterase-producing Lactobacillus fermentum and cellulase additives on the fermentation quality and microbial community of alfalfa silage.

Rina Su,Weixiong Shi,Xiaopan Yang,Jie Zhang,Chen Jie,Kuikui Ni,Liu Yan,Yayong Liu,Jin Zhong,Tianwei Wang

doi:10.7717/peerj.7712

Abstract

BackgroundAlfalfa (Medicago sativa) is an important forage material widely used for animal feed production. Ensiling is an effective method for preserving alfalfa, but it has shown some limitations in the production of high-quality alfalfa silage due to its low water soluble carbohydrates (WSC) content and high buffering capacity. Lactic acid bacteria (LAB) and cellulase are often used as silage additives to promote the ensiling process and enhance fermentation quality.MethodsExperiments were conducted to investigate the effects of ferulic acid esterase (FAE)-producing Lactobacillus fermentum 17SD-2 (LF) and cellulase (CE) on the fermentation quality and microbial community of alfalfa silage. After 60 days of ensiling, analysis of fermentation quality and bacterial diversity in alfalfa silages were conducted using high-performance liquid chromatography and high-throughput sequencing methods.ResultsAlfalfa was ensiled with additives (LF, CE, and LF+CE) or without additives for 60 days. All additives increased lactic acid and decreased pH values and ammonia-N contents compared to control. Among all treatments, the combined addition of LF and CE showed lowest pH (4.66) and ammonia-N (NH3-N, 0.57% DM) content, highest contents of lactic acid (LA, 10.51% DM), dry matter (DM, 22.54%) and crude protein (CP, 24.60% DM). Combined addition of LF and CE performed better in reducing neutral detergent fiber (NDF, 29.76% DM) and acid detergent fiber (ADF, 22.86% DM) contents than the addition of LF (33.71, 27.39% DM) or CE (32.07, 25.45% DM) alone. Moreover, the microbial analysis indicated that LF+CE treatments increased the abundance of desirable Lactobacillus and inhibited the growth of detrimental Enterobacter and Clostridia in alfalfa silage.DiscussionCombined addition of FAE-producing LF and CE is more effective than treatments of LF or CE alone in improving fermentation quality and nutrition values of alfalfa silage. This is likely due to a synergistic effect of CE and FAE produced by LF on plant cell wall degradation, indicating that these additives promote each other to improve fiber degradation and silage fermentation. In conclusion, combined addition of FAE-producing LF and CE could be a feasible way to improve alfalfa silage quality.

Highlights

Alfalfa is widely used for animal feed in the world due to its high protein content
In order to enhance fermentation quality, lactic acid bacteria (LAB) and cellulase are often used as silage additives
Compared with sample 1, lower Chao and Shannon indexes were observed in sample 2, which was consistent with the results reported by Wang et al (2018), indicated that wilting had an important influence on silage microorganism

Summary

Introduction

Alfalfa is widely used for animal feed in the world due to its high protein content. the low concentration of WSC and high buffering capacity in alfalfa makes it difficult to ensile for high silage quality (Silva et al, 2016). In order to enhance fermentation quality, lactic acid bacteria (LAB) and cellulase are often used as silage additives. Lactic acid bacteria (LAB) and cellulase are often used as silage additives to promote the ensiling process and enhance fermentation quality. Combined addition of FAE-producing LF and CE is more effective than treatments of LF or CE alone in improving fermentation quality and nutrition values of alfalfa silage. This is likely due to a synergistic effect of CE and FAE produced by LF on plant cell wall degradation, indicating that these additives promote each other to

Methods

Results

Conclusion