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...

BackgroundThe efficient utilization of lignocellulosic biomass for biofuel production has received increasing attention. Previous studies have investigated the pretreatment process of biomass, but the detailed enzymatic hydrolysis process of pretreated biomass remains largely unclear. Thus, this study investigated the pretreatment efficiency of dilute alkali, acid, hydrogen peroxide and its ultimate effects on enzymatic hydrolysis. Furthermore, to better understand the enzymatic digestion process of alkali-pretreated sweet sorghum straw (SSS), multimodal microscopy techniques were used to visualize the enzymatic hydrolysis process.ResultAfter pretreatment with alkali, an enzymatic hydrolysis efficiency of 86.44% was obtained, which increased by 99.54% compared to the untreated straw (43.23%). The FTIR, XRD and SEM characterization revealed a sequence of microstructural changes occurring in plant cell walls after pretreatment, including the destruction of lignin–polysaccharide interactions, the increase of porosity and crystallinity, and reduction of recalcitrance. During the course of hydrolysis, the cellulase dissolved the cell walls in the same manner and the digestion firstly occurred from the middle of cell walls and then toward the cell wall corners. The CLSM coupled with fluorescent labeling demonstrated that the sclerenchyma cells and vascular bundles in natural SSS were highly lignified, which caused the nonproductive bindings of cellulase on lignin. However, the efficient delignification significantly increased the accessibility and digestibility of cellulase to biomass, thereby improving the saccharification efficiency.ConclusionThis work will be helpful in investigating the biomass pretreatment and its structural characterization. In addition, the visualization results of the enzymatic hydrolysis process of pretreated lignocellulose could be used for guidance to explore the lignocellulosic biomass processing and large-scale biofuel production.