Effects of microbial enzymes on starch and hemicellulose degradation in total mixed ration silages

Abstract

ObjectiveThis study investigated the association of enzyme-producing microbes and their enzymes with starch and hemicellulose degradation during fermentation of total mixed ration (TMR) silage.MethodsThe TMRs were prepared with soybean curd residue, alfalfa hay (ATMR) or Leymus chinensis hay (LTMR), corn meal, soybean meal, vitamin-mineral supplements, and salt at a ratio of 25:40:30:4:0.5:0.5 on a dry matter basis. Laboratory-scale bag silos were randomly opened after 1, 3, 7, 14, 28, and 56 days of ensiling and subjected to analyses of fermentation quality, carbohydrates loss, microbial amylase and hemicellulase activities, succession of dominant amylolytic or hemicellulolytic microbes, and their microbial and enzymatic properties.ResultsBoth ATMR and LTMR silages were well preserved, with low pH and high lactic acid concentrations. In addition to the substantial loss of water soluble carbohydrates, loss of starch and hemicellulose was also observed in both TMR silages with prolonged ensiling. The microbial amylase activity remained detectable throughout the ensiling in both TMR silages, whereas the microbial hemicellulase activity progressively decreased until it was inactive at day 14 post-ensiling in both TMR silages. During the early stage of fermentation, the main amylase-producing microbes were Bacillus amyloliquefaciens (B. amyloliquefaciens), B. cereus, B. licheniformis, and B. subtilis in ATMR silage and B. flexus, B. licheniformis, and Paenibacillus xylanexedens (P. xylanexedens) in LTMR silage, whereas Enterococcus faecium was closely associated with starch hydrolysis at the later stage of fermentation in both TMR silages. B. amyloliquefaciens, B. licheniformis, and B. subtilis and B. licheniformis, B. pumilus, and P. xylanexedens were the main source of microbial hemicellulase during the early stage of fermentation in ATMR and LTMR silages, respectively.ConclusionThe microbial amylase contributes to starch hydrolysis during the ensiling process in both TMR silages, whereas the microbial hemicellulase participates in the hemicellulose degradation only at the early stage of ensiling.

Fermentation Profile, Nutritional Value, and Microbial Population of C4 Grasses Silages with or Without Bacterial Additive

“…These microorganisms have their activity intensified in the presence of soluble carbohydrates, acids, and proteins, increasing the silage pH (Table 4). The hemicellulose degradation has been neglected for many years (Ning et al, 2017), but some studies have shown this degradation occurs during the ensiling (Muck, 1990;Chen et al, 2015). Melvin (1965) and Yahaya et al (2001) reported that the degradation products of hemicellulose (xylose) and starch (glucose) could be substrates for microorganisms to produce acids during the ensiling; this fact was observed in our study (Table 2).…”

Effects of re‐ensiling on the fermentation quality and microbial community of napier grass (Pennisetum purpureum) silage

“…4). Bacillus pumilus can produce microbial enzymes that degrade plant structural carbohydrates during silage fermentation 38 . Furthermore, B. sonorensis was expected to be a potential source of endo‐glucanase and xylanase, which have potential applications in the saccharification of lignocellulosic biomass 39 .…”

Effects of Bacillus subtilis and its metabolites on corn silage quality

“…Recent studies have reported B. amyloliquefaciens , B. cereus , B. licheniformis , B. subtilis , B. flexus and B. pumilus as the main sources of microbial enzymes that degrade complex carbohydrates in mixed‐feed silage plants during fermentation (Ning et al . 2017).…”