There has been growing interest to develop forage rice as a new feed resource for livestock. This study was to characterize the natural population of lactic acid bacteria (LAB) and select potentially excellent strains for paddy rice silage preparation in China. One hundred and twenty-six strains were isolated and screened from paddy rice silage prepared using a small-scale fermentation system, and ninety-nine of these isolates were considered to be LAB based on their Gram-positive and catalase-negative morphology and the production of most of their metabolic products as lactic acid. These isolates were divided into eight groups (A-H) on the basis of their morphological and biochemical characteristics. The Group A to H strains were identified as Lactobacillus (L.) plantarum subsp. plantarum (species ratio: 8.1%), L. casei (5.1%), Leuconostoc (Ln.) pseudomesenteroides (11.1%), Pediococcus (P.) pentosaceus (24.2%), Enterococcus (E.) mundtii (12.1%), Lactococcus (Lc.) garvieae (15.2%), E. faecium (9.1%) and Lc. lactis subsp. lactis (15.2%) based on sequence analyses of their 16S rRNA and recA genes. P. pentosaceus was the most abundant member of the LAB population in the paddy rice silage. A selected strain, namely L. casei R 465, was found to be able to grow under low pH conditions and to improve the silage quality with low pH and a relatively high content of lactic acid. This study demonstrated that forage paddy rice silage contains abundant LAB species and its silage can be well preserved by inoculation with LAB, and that strain R 465 can be a potentially excellent inoculant for paddy rice silage.

Lactic acid bacteria (LAB), which are characterized by producing various functional metabolites, including antioxidants, organic acids, and antimicrobial compounds, are widely used in the food industry to improve gut health and prevent the growth of spoilage microorganisms. With the continual incidence of foodborne disease and advocacy of consumers for gut health, LAB have been designated as vital biopreservative agents in recent years. Therefore, LAB with excellent antimicrobial properties and environmental tolerance should be explored further. In this study, we focus on screening the LAB strains from a specialty pig (Bamei pig) feces of the Tibetan plateau region and determine their antimicrobial properties and environmental tolerance to evaluate their potential probiotic values. A total of 116 LAB strains were isolated, from which the LAB strain Qinghai (QP)28-1 was identified as Lactiplantibacillus (L.) plantarum subsp. plantarum using 16S rDNA sequencing and recA amplification, showing the best growth capacity, acid production capacities, environmental tolerance, hydrophobicity, antibiotic susceptibility, and bacteriocin production capacity. Furthermore, this strain inhibited the growth of multiple pathogens by producing organic acids and bacteriocin. These bacteriocin-encoding genes were identified using PCR amplification, including plnS, plnN, and plnW. In conclusion, bacteriocin-producing L. plantarum subsp. plantarum QP28-1 stands out among these 116 LAB strains, and was considered to be a promising strain used for LAB-related food fermentation. Moreover, this study provides a convenient, comprehensive, and shareable profile for screening of superior functional and bacteriocin-producing LAB strains, which can be used in the food industry.

Winter wheat is a suitable crop to be ensiled for animal feed and China has the largest planting area of this crop in the world. During the ensiling process, lactic acid bacteria (LAB) play the most important role in the fermentation. We investigated the natural population of LAB in whole-crop wheat (WCW) and examined the quality of whole-crop wheat silage (WCWS) with and without LAB inoculants. Two Lactobacillus plantarum subsp. plantarum strains, Zhengzhou University 1 (ZZU 1) selected from corn and forage and grass 1 (FG 1) from a commercial inoculant, were used as additives. The silages inoculated with LAB strains (ZZU 1 and FG 1) were better preserved than the control, with lower pH values (3.5 and 3.6, respectively) (p<0.05) and higher contents of lactic acid (37.5 and 34.0 g/kg of fresh matter (FM), respectively) (p<0.05) than the control. Sixty LAB strains were isolated from fresh material and WCWS without any LAB inoculation. These LAB strains were divided into the following four genera and six species based on their phenotypic, biochemical and phylogenetic characteristics: Leuconostoc pseudomesenteroides, Leuconostoc citreum, Weissella cibaria, Lactococcus lactis subsp. lactis, Lactobacillus buchneri, and Lactobacillus plantarum subsp. plantarum. However, the prevalent LAB, which was predominantly heterofermentative (66.7%), consisted of Leuconostoc pseudomesenteroides, Leuconostoc citreum, Weissella cibaria, and Lactobacillus buchneri. This study revealed that most of isolated LAB strains from control WCWS were heterofermentative and could not grow well at low pH condition; the selective inoculants of Lactobacillus strains, especially ZZU 1, could improve WCWS quality significantly.

The contamination of fermented feeds and foods with fungi and mycotoxins is a major food safety issue worldwide. Certain lactic acid bacteria (LAB), generally recognized as safe (GRAS) fermentation probiotics, are able to reduce microbial and mycotoxins contamination. In this study, Lactiplantibacillus (L.) plantarum Q1-2 and L. salivarius Q27-2 with antifungal properties were screened as inoculants for mixed fermenting feed, and the fermentation and nutritional qualities, microbial community, and mycotoxins of mixed fermented feed were analyzed at different fermentation periods (1, 3, 7, 15, and 30 days, respectively). The findings indicated that the utilization of Q1-2 and Q27-2 strains in fermenting feed led to a decrease in pH and an increase in lactic acid concentration and the proportion of Lactiplantibacillus, while effectively restraining the proliferation of undesirable microorganisms. In particular, Q1-2 reduced the relative abundance of fungi including Fusarium and Aspergillus. Compared to the control group, the Q1-2 and Q27-2 groups reduced aflatoxin B1 by 34.17% and 16.57%, and deoxynivalenol by up to 90.61% and 51.03%. In short, these two LAB inoculants could reduce the contents of aflatoxin B1 and deoxynivalenol to the limited content levels stipulated by the Chinese National Standard GB 13078-2017. These findings suggest that the LAB strains of Q1-2 and Q27-2 have potential applications in the feed industry for the mitigation of mycotoxin pollution, thereby enhancing the quality of animal feed.

For screening excellent lactic acid bacteria (LAB) strains to inhibit enterotoxigenic Escherichia coli (ETEC) K88, inhibitory activities of more than 1100 LAB strains isolated from different materials, and kept in the lab, were evaluated in this study. Nine strains with inhibition zones, at least 22.00 mm (including that of a hole puncher, 10.00 mm), and good physiological and biochemical characteristics identified by 16S DNA gene sequencing and recA gene multiple detection, were assigned to Lactobacillus (L.) plantarum subsp. plantarum (5), L. fermentum (1), L. reuteri (1), Weissella cibaria (1) and Enterococcus faecalis (1), respectively. As investigated for their tolerance abilities and safety, only strain ZA3 possessed high hydrophobicity and auto-aggregation abilities, had high survival rate in low pH, bile salt environment, and gastrointestinal (GI) fluids, was sensitive to ampicillin, and resistant to norfloxacin and amikacin, without hemolytic activity, and did not carry antibiotic resistance genes, but exhibited broad spectrum activity against a wide range of microorganisms. Antibacterial substance may attribute to organic acids, especially lactic acid and acetic acid. The results indicated that the selected strain L. plantarum subsp. plantarum ZA3 could be considered a potential probiotic to inhibit ETEC K88 in weaned piglets for further research.