Screening of natural lactic acid bacteria with potential effect on silage fermentation, aerobic stability and aflatoxin B1 in hot and humid area

Aim: To effectively make high-quality silage in hot and humid area.

Methods and results: The natural lactic acid bacteria (LAB) strains CZ149, XH358, XH753 and XH761 isolated from corn and Napier grass were screened by the potential of low pH growth and high lactic acid production, and their effect on silage quality, aerobic stability and aflatoxin B1 production of whole-crop corn was also studied in Sichuan, China. Four selected strains were Gram-positive and catalase-negative, rod-shaped strains that are able to grow at pH 3·5 and at 45°C. Strains CZ149, XH358, XH753 and XH761 were identified as Lactobacillus plantarum, L. salivarius, L. rhamnosus and L. paracasei, respectively. After 60 days of fermentation, all LAB strains showed no significant relationship with the quality of corn silage, whereas the lowest aflatoxin B1 and lactic-to-acetic ratio were detected in strain XH753-treated silage. Strain CZ149-treated silage showed worse aerobic stability and higher aflatoxin B1 concentration than control, whereas strain XH753-treated silage had better aerobic stability and lowest aflatoxin B1 concentration after aerobic exposure in hot and humid condition for 5 days.

Conclusions: The three L. plantarum strains used in this study are not suitable as inoculants for local whole-crop corn silage, whereas L. rhamnosus 753 could prolong the aerobic stability and inhibit the accumulation of aflatoxin B1 at hot and humid condition.

Significance and impact of the study: This study provides new information of LAB inoculants for corn silage in hot and humid areas. Especially, a screened strain of Lactobacillus rhamnosus 753 can be used as a candidate strains to make high-quality silage in tropical and subtropical areas.