Various pretreatments are employed to increase the utilization of rice straw as a ruminant feed ingredient to minimize its negative environmental impact. However, an efficient alternative is still needed. The purpose of this study was to evaluate the ability of ammonia and/or white-rot fungi (Pleurotus ostreatus) to degrade lignin, increase the nutritional value, and enhance the rumen fermentability of rice straw. Rice straw was treated with ammonia and/or basidiomycete white-rot fungi (P. ostreatus) with untreated straw as control under solid-state fermentation employing a completely randomized design. The crude protein increased from 2.05% in the control to 3.47% in ammoniated rice straw, 5.24% in basidiomycete white-rot fungi (P. ostreatus), and 6.58% in ammoniated-basidiomycete white-rot fungi-treated (P. ostreatus) rice straw. The ammoniated-basidiomycete white-rot fungi-treated (P. ostreatus) rice straw had the least lignin content (3.76%). Ammoniated-basidiomycete white-rot fungi-treated (P. ostreatus) rice straw had improved in vitro dry matter digestibility (65.52%), total volatile fatty acid (76.56 mM), and total gas production (56.78 mL/g) compared to ammoniated rice straw (56.16%, 67.71 mM, 44.30 mL/g) or basidiomycete white-rot fungi-treated (P. ostreatus) rice straw (61.12%, 75.36 mM, 49.31 mL/g), respectively. The ammoniated-basidiomycete white-rot fungi (P. ostreatus) treatment improved rice straw’s nutritional value, in vitro dry matter digestibility, volatile fatty acids, and gas production.

Lactic acid bacteria (LAB) is a collective term for bacteria capable of producing lactic acid from fermentable carbohydrates. Despite their widespread presence in the gastrointestinal tracts of humans and animals, where they play important physiological roles, functional analysis of specific strains from particular sources requires further enrichment. The objective of this study was to explore the differences between Pediococcus acidilactici OM681363 and Lacticaseibacillus paracasei ON606241, both isolated from the rumen of Chinese Holstein dairy cows, using whole-genome sequencing. The results indicate that P. acidilactici OM681363 contained three CRISPR fragments and numerous enzymes involved in carbohydrate degradation. Additionally, P. acidilactici OM681363 possessed more genes related to fiber degradation, especially cellobiose, and the sole carbon source experiment also confirmed this. However, it lacked genes associated with polysaccharide lyase. In contrast, L. paracasei ON606241 was found to be more specialized in breaking down non-fiber carbohydrates, producing more acetic and lactic acids. Overall, P. acidilactici OM681363 may have a greater capacity to degrade complex carbohydrates, while L. paracasei ON606241 appears to specifically target non-fiber carbohydrates.

Rumen bacteria have the ability to efficiently degrade and acidify lignocellulosic biomass, among which rumen solid-phase bacteria are more dominant. However, the effectiveness of in vitro cultured ruminal solid-phase bacteria in producing volatile fatty acids (VFA) during lignocellulosic biomass degradation remains unclear. This study presents a feasibility analysis of the long-term subculture of rumen solid-phase bacteria in vitro for VFA production. The results indicated that VFA production could reach 0.20–0.30 g/g dry matter. After 40 generations (200 days) of subculturing, the bacterial community underwent alterations. The relative abundance of certain fiber-degrading, acid-producing bacteria, which were less abundant in rumen solids, such as Oribacterium and Victivallis, was significantly upregulated following subculturing in vitro. The success of this study in subculturing rumen solid-phase bacteria in vitro over an extended period and achieving efficient VFA production is of considerable importance for the practical application of rumen microorganisms in production settings.