Effect of psychrotrophic Lactiplantibacillus plantarum L75 with exoploysaccharides-producing property on fermentation, bacterial community, and antioxidant activity of oat silage at low temperature

The low temperature during oat harvesting season in the Qinghai-Tibet Plateau (QTP) is a primary challenge for successful silage fermentation. This study aimed to investigate the effect of a psychrotrophic Lactiplantibacillus plantarum (L. plantarum) L75 strain with exoploysaccharides (EPS)-producing property on fermentation quality, bacterial community, and antioxidant activity of oat silage ensiled at low temperature. The freshly chopped oat was subjected to three different treatments: ⅰ) no inoculation (control); ⅱ) inoculated with psychrotrophic L. plantarum L75, possessing EPS-producing properties; ⅲ) inoculated with a commercial inoculant L. plantarum. All inoculants were applied at a rate of 1 × 10⁵ cfu/g on a fresh matter basis, and then ensiled at 25, 15, and 10℃, respectively. Results indicated that the strain L75 exhibited better performance in EPS production, growth rate, and acid production compared to the commercial inoculant at low temperature. Inoculating with both strains improved the silage quality of oat forage by enhancing fermentation quality and suppressing undesirable microorganisms such as Hafnia alvei and Ewingella americana throughout the fermentation process compared to the control silage. Importantly, L75 was more effective than the commercial inoculant in enhancing fermentation quality, antioxidant activity, and the proportion of Lactiplantibacillus plantarum, leading to lower dry matter loss of oat silages at low temperature. In conclusion, the psychrotrophic strain L75 with EPS-producing property has great potential to improve fermentation quality and antioxidant activities of oat silage by altering bacterial composition at low temperatures. Thus, strain L75 can be used as a candidate strain for making high-quality silage in alpine region with low temperature in forage harvesting season.