A slow-release strategy of Lactobacillus plantarum to enhance the degradation of cellulose by Bacillus methylotrophic in the ensiling process of corn stalk.

Abstract

The enhancement of cellulose degradation is important for improving the quality of corn-stalk silage. However, the rapid drop in pH caused by the propagation of lactic acid bacteria (LAB) can influence the degradation of cellulose by cellulose-degrading microorganisms (CDMs) during the mixed fermentation process of ensilage. In this study, a CDM (Bacillus methylotrophic 2-4, BM 2-4) was isolated, and its lyophilization condition was studied. Moreover, a slow-release strategy was developed to delay the release of LAB (Lactobacillus plantarum S-1, LP S-1) by embedding technology to provide time for BM 2-4 to degrade cellulose during the corn-stalk ensilage process. The results showed that BM 2-4 had a higher survival rate (89.53%) under the following conditions: cell collection (5,600 r/min in 4.4°C for 9.5-min centrifugation) and lyophilization using cryoprotectants [skim milk (10.4%), peptone (10.4%), and glucose (5.2%)] at -50°C with a vacuum pressure of <10 Pa. Based on the results of the previous study on embedded LP S-1, simultaneous inoculation of embedded LP S-1 and lyophilized BM2-4 at a 2:1 ratio, with an inoculum size of 6% and moisture content of 85%, significantly degraded CF by 3.8% and increased CP by 3.7% (p < 0.05). This treatment did not significantly influence the final pH of corn-stalk silage (p > 0.05) after 7 days of fermentation.