Effects of microbial inoculants on the fermentation characteristics and microbial communities of sweet sorghum bagasse silage

Abstract

Sweet sorghum bagasse (SSB) is a promising raw material for silage fermentation due to its high residual nutritive, but the efficient fermentation strategy of SSB has not been reported yet. This study evaluated the effects of microbial inoculant on the fermentation quality, chemical composition and microbial community of SSB silage. The silage inoculated with isolated lactic acid bacteria (LpE) achieved better fermentation than that of commercial inoculant A, B (CIA, CIB) and untreatment, including low pH value, high levels of lactic acid and water soluble carbohydrates (WSC) content, which demonstrated that the LpE inoculant could contribute to the preservation of nutrition and the manipulation of fermentation process of SSB. In addition, the results of microbial community analysis indicated that the LpE inoculant significantly changed the composition and diversity of bacteria in SSB silage. After ensiling, the LpE inoculated silage were dominated by Lactobacillus(95.71%), Weissella(0.19%). These results were of great guiding significance aiming for high-quality silage production using SSB materials on the basis of target-based regulation methods. Sweet sorghum (Sorghum bicolor (L.) Moench) is a low-cost non-food energy crop that can simultaneously produce the sugar juice and bagasse 1. In addition, the sweet sorghum has a high photosynthetic efficiency resulted in high biomass productivity and rapid accumulation of sugars in stems 2,3. It also has a remarkable stress tolerance in harsh growth conditions, such as salinity, alkalinity and drought areas 4,5. Currently, the utilization of sweet sorghum mainly focused on the juice fermentation for biofuels and chemicals production because the juice extracted from sweet sorghum stems contains high sugar contents and could be fermented directly by microbes 6,7. Hence, a large amount of sweet sorghum bagasse (SSB) will be certainly left from the industrial-scale extraction of sugar juice to meet the needs of fermentation industry. Although the SSB was used as a substrate for burning, converting to cellulosic sugars, producing biofuels and structural materials 8-10 , it remains underutilized at current stage. While ensiling is an efficient approach to fermenting sweet sorghum bagasse and used for animal feeds 11. During ensiling process, the lactic acid bacteria (LAB) and water soluble carbohydrate (WSC) are important factors for achieving high quality silage fermentation 12,13. Thus, the production of high quality silage from sweet sorghum bagasse is a good choice due to its high residual nutritive and sugars, and low cost 10. The LAB inoculant have been proposed as an effective additives to prolong the storage time and improve the feed palatability 14,15. The present study also uses two LAB strains (NCBI Accession No. MN022576 and MN022577) as additive, isolated from corn silage. Besides, the application of LAB isolated from forage crops for SSB silage fermentation has not been reported. In general, silage fermentation is a fully microbial-based fermentation process 1...

Assessment of Bacterial Community Composition and Dynamics in Alfalfa Silages With and Without Lactobacillus plantarum Inoculation Using Absolute Quantification 16S rRNA Sequencing

“…These genera were mainly observed in the CK group. These results were in accordance with former studies reported by Ogunade et al (2018) , Yang et al (2019) , and Dong et al (2020) . Hetero-fermentative LAB like Weissella are less efficient in decreasing pH than homofermentative Lactobacillus .…”

“…AQS accurately illustrated the dynamics in absolute abundance of bacterial community in alfalfa silage using synthetic chimeric DNA spikes, and uncovered more sequencing information analyzing alpha and beta diversities of bacterial communities than RQS. Dong et al (2020) reported a reduction in richness of bacterial community through the ensiling process in Broussonetia papyrifera and perennial ryegrass mixed silage. Similarly, bacterial richness indices in our study reduced at 60days compared with the 10-day alfalfa silage.…”

Microbial community dynamics during alfalfa silage with or without clostridial fermentation

“…Lactobacillus plantarum (LP) and sucrose (S) are widely used to promote lactic acid fermentation and restrict clostridial fermentation, which improvs the silage quality of moist forage crops 15 , 16 . Most previous studies only reported how changes in the bacterial community affect the quality of silage 6 , 17 , 18 , whereas the effects of these additives on clostridial diversity are unclear. We previously analyzed the clostridial community dynamics of alfalfa silage following addition of both LP and S. However, the clostridial community dynamics were not detected when LP or S was added separately.…”

Effect of microbial inoculants on the chemical composition and aerobic stability of Tanzania guinea grass silages

“…Both inoculants were effective in reducing the pH relative to the control silage. Sufficient concentrations of soluble carbohydrates are required as the fuel for lactic acid bacteria (Tomaz et al, 2018;Dong et al, 2020). When this condition is met, the bacteria present in the inoculants produce lactic acid and acetic acid, resulting in lowered pH (Holzer et al, 2003).…”

“…However, the results of these studies have been contradictory and inconclusive. It is believed that differences among the strains of bacteria that were used contributed to the disparate effects (Dong et al, 2020). Ávila et al (2009) described improvements in the fermentation profile and reduction of fungi concentration in Mombaça guinea grass silage that was inoculated with Lactobacillus buchneri.…”