Growing interest has been focused on lactic acid bacteria as alternatives to antimicrobial growth promoters, which are characterized by the production of various functional metabolites, such as antimicrobial and antioxidants compounds. The present study was undertaken to evaluate a potential probiotic from the antioxidant perspective. LC-9-1, screened from the intestines of healthy animals, was revealed to be Pediococcus acidilactici on the basis of its morphological, biochemical, and molecular characteristics. The strain has excellent properties, including acid-production efficiency, antibacterial performance and antioxidant activity. The safety of the strain was also evaluated. Furthermore, the experiments in broiler chickens suggested that dietary LC-9-1 supplementation improved the growth performance and decreased the abdominal fat, and enhanced the antioxidant capability and intestinal innate immunity of broilers. Analysis of intestinal microbiota showed that a higher community diversity (Shannon index) was achieved. In addition to the significantly increased relative abundances of Pediococcus spp., beneficial genera such as Rothia spp. and Ruminococcus spp. were abundant, while opportunistic pathogens such as Escherichia-Shigella spp. were significantly reduced in LC-9-1-supplemented broilers. Collectively, such in-depth characterization and the available data will guide future efforts to develop next-generation probiotics, and LC-9-1 could be considered a potential strain for further utilization in direct-fed microbial or starter culture for fermentation.

The poultry industry has been and is still suffering considerable challenges because of the increasing price of soybean meal. Therefore, it is imperative to find alternative, high-quality plant protein sources. Peanut meal (PNM), a by-product of peanut oil extraction, is abundant in crude protein (40.1–50.9%), making it a potential plant protein source. However, nutritional and non-nutritional limitations are detrimental to its application in poultry diets, such as an imbalance in amino acid composition, phytate and the risk of aflatoxins pollution. As a processing technique, solid-state fermentation has been used to reduce phytate and improve the nutrient availability of plant protein sources in the feed industry. It is a promising approach to improving the application of PNM in poultry diets. There are several advantages to the solid-state fermentation of PNM, such as low-cost equipment, high productivity, the stability of the product and the minimization of energy consumption. Currently, there is still a lack of synthesized information on the application of solid-state fermented PNM in poultry. This review summarized the limiting factors for PNM application in poultry feed and the improvement of solid-state fermentation on the nutritional value of plant protein sources so as to evaluate the feasibility of improving the nutritional value of PNM as poultry feed through solid-state fermentation. We hope to shed some light on the selection of protein resources in future research.

Peanut meal (PNM) is a byproduct of the peanut oil extraction process, but its application is seriously limited by the presence of anti-nutritional factors, imbalance in amino acid profiles, and susceptibility to mycotoxin contamination. This study was conducted to investigate the effects of solid-state fermentation on the nutritional quality of PNM, as well as the effects of PNM and fermented peanut meal (FPNM) on the ileal digestibility of amino acids and apparent metabolizable energy (AME) of broiler chickens. The results indicated that the fermentation improved the quality of PNM by increasing the crude protein, TCA-soluble protein, and L-lactic acid concentration (p < 0.05), and decreasing the crude fiber, phytic acid, and aflatoxin B₁ concentration (p < 0.05). Solid-state fermentation also increased the free amino acids level and improved the balance of hydrolyzed amino acids of PNM. A nitrogen-free diet was used to determine the loss of endogenous amino acid in birds, and the PNM or FPNM as the only protein source to formulate semi-purified diets. The result showed that feeding on FPNM resulted in higher apparent ileal digestibility (AID) and standardized ileal digestibility (SID) values of the essential amino acids of methionine, lysine, leucine, and phenylalanine (p < 0.05). Moreover, the AID and SID values of the non-essential amino acids of FPNM were both higher than those of PNM, except for proline (p < 0.05). The AME was determined by the classic substitution method, and the results showed that fermentation had no effect on the AME value (p > 0.05). In conclusion, solid-state fermentation improved the nutritional value of PNM, and FPNM was a potential ingredient as an alternative protein source for broilers.

Inorganic polyphosphate (PolyP) is a high-molecular-weight polymer that plays multiple roles in regulating immune responses. However, the specific anti-inflammatory mechanisms of bacteria-derived PolyP are unclear. In the present study, PolyP was extracted from Lactobacillus plantarum (L. plantarum), and the chain length was estimated to be approximately 250 Pi residues. The immune regulatory functions of PolyP were investigated using a lipopolysaccharide (LPS)-induced RAW264.7 cell oxidative stress model, and dexamethasone was used as a positive control. The result revealed that both dexamethasone and PolyP were protective against oxidative stress by inhibiting macrophage M1 polarization and the production of several markers, such as nitric oxide (NO), reactive oxygen species (ROS), inducible nitric oxide synthase (iNOS), and cyclooxygenase (COX)-2. In addition, PolyP suppressed inflammation progression by regulating the production of several cytokines, such as interleukin (IL)-1β, interferon (INF)-γ, tumor necrosis factor (TNF)-α, and IL-6, and inhibited the expressions of inhibitory κB kinase (IKK) α, IKKβ, and extracellular regulated protein kinases 2 (ERK2). Conclusively, PolyP derived from L. plantarum has the ability to protect cells from oxidative stress damage by inhibiting M1 polarization in macrophages. These findings provide insights into the function of PolyP and offer support for the potential application of PolyP in immune-related diseases.

Peptidoglycan (PGN) is a unique component of prokaryotic cell walls with immune-enhancing capacities. Here, we extracted PGN from Corynebacterium glutamicum, a by-product of amino acid fermentation, using the trichloroacetic acid (TCA) method. SDS-PAGE analysis confirmed the presence of PGN, with a band of approximately 28 kDa. Further analysis was conducted through amino acid analysis, FTIR, and MALDI-TOF/TOF MS, and the results showed that the chemical structural monomer of PGN is NAG-(β-1,4-)-NAM-l-Ala-d-Glu-l-Lis-d-Ala. The immune activation effects of PGN were evaluated in a RAW264.7 cell model. Our results showed that PGN could increase the secretion level of NO, ROS, and immune regulatory substances, including TNF-α and IL-1β, and up-regulated the mRNA expression of TNF-α and iNOS. In addition, PGN stimulated the expression of ERK2, MyD88, RIP2, and the related receptor NOD1 in the NF-κB and MAPK pathways. Comparative RNA sequencing was conducted to analyze the gene expression profiles in RAW264.7 cells. KEGG analysis indicated that most of the genes were enriched in the NF-κB, MAPK, and TNF signaling pathways. Taken together, these findings suggest that PGN may have immune-activating potential for the development and application of immune adjuvants. Importantly, the application of PGN also provides a new way to utilize amino acid fermentation by-products.