Microbial network and fermentation modulation of Napier grass and sugarcane top silage in southern Africa

Abstract

ABSTRACT To effectively alleviate the shortage of animal feed in the tropics, we applied a screening lactic acid bacteria (LAB) strain (Lactiplantibacillus plantarum MO1) and a commercial inoculant (L. plantarum LP1) to prepare silage from early flowering Napier grass and after harvest sugarcane tops in southern Africa. The microbial community structure, co-occurrence network, and fermentation characteristics of silage were analyzed using PacBio single-molecule real-time sequencing technology. Strain MO1, isolated from corn silage, was characterized by strong acid tolerance and the ability to produce lactic acid. Before ensiling, the dominant microbial community in both Napier grass and sugarcane top were Gram-negative harmful microbes. After ensiling, the main microbial community shifted from Gram-negative to Gram-positive bacteria, and the microbial alpha diversity of all silages significantly decreased (P < 0.05). Compared to the control, fermentation of the LAB-treated silages was accelerated and L. plantarum became the dominant microbial community, while the lactic acid content increased (P < 0.05) and the pH was reduced (P < 0.05). In the MO1-treated silages, the relative abundance of LAB was markedly increased and formed a co-occurrence microbial network with L. plantarum as the dominant microorganism. It also led to the global and overview maps, as a special class of metabolic pathways in the Kyoto Encyclopedia of Genes and Genomes database was enhanced and the carbohydrate metabolism and amino acid metabolism pathways were weakened, thereby improving the flavor and quality of the silages compared to the LP1-treated ones. Strain MO1 can modulate the microbial community and metabolic pathways and achieve clean fermentation. It is of great significance to alleviate feed shortage and promote sustainable production of livestock. IMPORTANCE Feed shortage in the tropics is a major constraint to the production of livestock products such as milk and meat. In order to effectively utilize of local feed resources, the selected lactic acid bacteria (LAB) strain was used to prepare Napier grass and sugarcane top silage. The results showed that the two silages inoculated with LAB formed a co-occurrence microbial network dominated by Lactiplantibacillus during the fermentation process, regulated the microbial community structure and metabolic pathways, and improved the silage fermentation quality. This is of great significance for alleviating feed shortage and promoting sustainable production of livestock.

Keywords

• fermentation modulation
• lactic acid bacteria screening
• microbial co-occurrence network
• PacBio SMRT
• tropical silage