Characteristics of proteolytic microorganisms and their effects on proteolysis in total mixed ration silages of soybean curd residue

Abstract

Objective: The objective of this study was to isolate proteolytic microorganisms and evaluate their effects on proteolysis in total mixed ration (TMR) silages of soybean curd residue. Methods: TMRs were formulated with soybean curd residue, alfalfa or Leymus chinensis hay, corn meal, soybean meal, a vitamin-mineral supplement, and salt in a ratio of 25.0: 40.0:30.0:4.0:0.5:0.5, respectively, on a basis of dry matter. The microbial proteinases during ensil ing were characterized, the dominate strains associated with proteolysis were identified, and their enzymatic characterization were evaluated in alfalfa (A-TMR) and Leymus chinensis (L-TMR) TMR silages containing soybean curd residue. Results: Both A-TMR and L-TMR silages were well preserved, with low pH and high lactic acid concentrations. The aerobic bacteria and yeast counts in both TMR silages decreased to about 10 5 cfu/g fresh matter (FM) and below the detection limit, respectively. The lactic acid bacteria count increased to 10 9 cfu/g FM. The total microbial proteinases activities reached their maximums during the early ensiling stage and then reduced in both TMR silages with fermentation prolonged. Metalloproteinase was the main proteinase when the total proteinases activities reached their maximums, and when ensiling terminated, metallo and serine proteinases played equally important parts in proteolysis in both TMR silages. Strains in the genera Curtobacterium and Paenibacillus were identified as the most dominant proteolytic bacteria in A-TMR and L-TMR, respectively, and both their proteinases were mainly with metalloproteinase characteristics. In the latter ensiling phase, Enterococcus faecium strains became the major sources of proteolytic enzymes in both TMR silages. Their proteinases were mainly of metallo and serine proteinases classes in this experiment. Conclusion: Proteolytic aerobic bacteria were substituted by proteolytic lactic acid bacteria during ensiling, and the microbial serine and metallo proteinases in these strains played leading roles in proteolysis in TMR silages.

Replacing Alfalfa with Paper Mulberry in Total Mixed Ration Silages: Effects on Ensiling Characteristics, Protein Degradation, and In Vitro Digestibility

“…In terms of forage crops, especially for high-protein herbages, it is inevitable that large quantities of true protein are converted into NPN during ensiling, resulting in poor nitrogen utilization for ruminants. In the present study, NPN content in all silages increased rapidly during the first 7 days of ensiling, as supported by Hao et al [ 34 ] in TMR silages. However, higher NPN content with lower silage pH in RY36 compared with RY0 is in agreement with Sousa et al [ 35 ], who reported that protein breakdown during ensiling can be reduced by a rapid decrease in silage pH.…”

Characterization of phyllosphere endophytic lactic acid bacteria reveals a potential novel route to enhance silage fermentation quality

“…Meanwhile, the activity of arginase, a key enzyme in the urea cycle 45 , was also obviously lower than that in natural silage. According to the findings of Hao et al 46 , protein-degrading bacteria in silage mainly included Curtobacterium, Bacillus, Paenibacillus , Enterococcus, Pediococcus and Lactiplantibacillus , with the highest proteinase activity in Bacillus, Enterococcus , Clostridium and Enterobacter . According to the results, free amino acids produced by microorganisms through protein hydrolysis should be balanced with their amino acid and nucleotide metabolism as available nitrogen sources.…”

Investigating the efficacy of an exopolysaccharide (EPS)‐producing strain Lactiplantibacillus plantarum L75 on oat silage fermentation at different temperatures

“…( 2022 ), who disclosed that Weissella , accompanied by a certain proportion of Serratia and Pantoea presented in graminaceous crop (whole‐plant corn). As another dominant genera, Curtobacterium was proved as the proteolytic bacteria in the alfalfa and Leymus chinensis silages (Hao et al., 2020 ). Gharechahi et al.…”

“…This agrees with the result of Bai et al (2022), who disclosed that Weissella, accompanied by a certain proportion of Serratia and Pantoea presented in graminaceous crop (whole-plant corn). As another dominant genera, Curtobacterium was proved as the proteolytic bacteria in the alfalfa and Leymus chinensis silages (Hao et al, 2020). Gharechahi et al (2017) ever stated that the microbial community, which develops during the fermentation process, varies distinctly from that of epiphytic one.…”