Identification and isolation of Lactobacillus fructivorans from wilted alfalfa silage with and without molasses

Effect of different dry matter content on fermentation characteristics and nutritional quality of Napier grass silage with novel lactic acid bacteria strains

To investigate the characteristics of different LAB strains isolated from subtropics and their effects on Napier grass (Pennisetum purpureum Schum.) silage with two dry matter (DM) levels, sugar fermentation pattern, and growth profiles of three screened lactic acid bacteria (LAB) strains [Pediococcus pentosaceus (PP04), Weissella cibaria (WC10), and Lactobacillus plantarum (LP694)] were characterized, and then used either individually or in combination at 1.0 × 106 cfu g-1 fresh weight to inoculate grass having 15% or 25% DM. Treatments were applied: (1) no inoculant (control); (2) PP04; (3) WC10; (4) LP694; (5) M-1 (PP04: WC10 = 2:1); (6) M-2 (PP04: LP694 = 1:2); (7) M-3 (WC10: LP694 = 2:1); (8) M-4 (PP04: WC10: LP694 = 2:1:1). The results showed that all inoculations increased LAB, DM recovery, and lactic acid (LA) concentration, while decreasing pH, the ammonia nitrogen/total nitrogen (NH3-N/TN), and butyric acid (BA) concentration compared to control group in both DM. However, the effect of inoculations was very limited at 15% DM. Silages with inoculants achieved higher silage quality at 25% DM than 15% DM. The different LAB inoculants result in significant differences in silage quality, while W. cibaria decreased the pH and inhibited the growth of undesirable bacteria and those characteristics were not affected by the DM content.

Varieties and ensiling: Impact on chemical composition, fermentation quality and bacterial community of alfalfa

Introduction

Six species of alfalfa commonly found in northern China were collected in the present study.

Methods

The chemical composition and epiphytic microbial communities during the ensiling were analyzed; and their effects on fermentation quality and silage bacterial communities were assessed. The effects of physicochemical characteristics of alfalfa on the bacterial community were also investigated in terms of nutritional sources of microbial growth and reproduction.

Results and discussion

The results showed that the chemical composition was significantly different in various alfalfa varieties, yet, the dominant genera attached to each variety of alfalfa was similar, except for pantoea (p<0.05). After ensiling, both the fermentation quality and microbial community changed obviously (p<0.05). Specifically, ZM2 had lower pH and ammonia nitrogen (NH₃-N) content but higher LA content than other varieties of alfalfa silage. Beneficial bacteria such as Lentilactobacillus and Lactiplantibacillus were predominant in ZM2, which accounted for the higher fermentation quality. Significant correlations between the chemical composition of silage, fermentation quality and bacterial communities composition were observed. Moreover, variations in bacteria community structure during the fermentation of alfalfa were mainly influenced by water-soluble carbohydrates (36.79%) and dry matter (21.77%).

Conclusion

In conclusion, this study revealed the influence of chemical composition on microbial community and fermentation quality, laying the groundwork for future studies on high-quality silage.

Advances in characterization of probiotics and challenges in industrial application

An unbalanced diet and poor lifestyle are common reasons for numerous health complications in humans. Probiotics are known to provide substantial benefits to human health by producing several bioactive compounds, vitamins, short-chain fatty acids and short peptides. Diets that contain probiotics are limited to curd, yoghurt, kefir, kimchi, etc. However, exploring the identification of more potential probiotics and enhancing their commercial application to improve the nutritional quality would be a significant step to utilizing the maximum benefits. The complex evolution patterns among the probiotics are the hurdles in their characterization and adequate application in the industries and dairy products. This article has mainly discussed the molecular methods of characterization that are based on the analysis of ribosomal RNA, whole genome, and protein markers and profiles. It also has critically emphasized the emerging challenges in industrial applications of probiotics.

Effects of inoculation of Lactiplantibacillus plantarum and Lentilactobacillus buchneri on fermentation quality, aerobic stability, and microbial community dynamics of wilted Leymus chinensis silage

Leymus chinensis is an important crop that can be fed to ruminants. The purpose of this study was to investigate the roles of Lactiplantibacillus plantarum and Lentilactobacillus buchneri in fermentation quality, aerobic stability, and dynamics of wilted L. chinensis silage microorganisms. Wilted L. chinensis silages were ensiled with/without L. plantarum and L. buchneri. After 14 and 56 days of ensiling, the silos were opened and subjected to a 7-day aerobic deterioration test. This study looked at the composition of fermentation products as well as the microbial communities in silage. Silage inoculated with L. plantarum and L. buchneri had an increased lactic acid content as well as lactic acid bacterial (LAB) quantity, but a decrease in pH and levels of butyric acid, 2,3-butanediol, and ethanol was observed during ensiling. Non-treated and L. plantarum-treated silages deteriorated in the 7-day spoilage test after opening day-14 silos, whereas L. buchneri-inoculated silage showed no signs of deterioration. Lactobacillus abundance increased in the 7-day spoilage test after opening day-56 silos, while undesirable microorganisms such as Acetobacter, Bacillus, and molds, namely, Aspergillus and Penicillium were inhibited within L. plantarum- and L. buchneri-inoculated silages. The composition of fermentation products was related to the bacterial community, particularly Lactobacillus, Enterococcus, and Acetobacter. To summarize, L. plantarum- and L. buchneri-inoculated silage enhanced fermentation quality during ensiling and inhibited aerobic spoilage in a 7-day spoilage test of 56 days ensiling within wilted L. chinensis silage.

Lactobacillus plantarum and molasses alter dynamic chemical composition, microbial community, and aerobic stability of mixed (amaranth and rice straw) silage

BACKGROUND

The objective was to determine how molasses and Lactobacillus plantarum affect chemical composition, fermentation quality, aerobic stability, and the microbial community of an ensiled mixture of amaranth (Amaranthus hypochondriaus, AF) and rice straw. Treatments were control (C, no addition), L. plantarum (L; 2 × 10⁵  cfu g^-1 fresh weight), molasses (M; 40 g kg^-1 fresh matter), and their combination (LM). All treatments were ensiled for 1, 3, 5, 7, and 30 days.

RESULTS

All additives improved fermentation quality with greater lactic acid (LA), acetic acid, and lower pH than C silage over the ensiling period. The LM silage combination optimized fermentability, manifested as greater LA contents and a more rapid pH reduction during the first 7 days of ensiling than L or M silages. After 30 days of ensiling, inoculant L. plantarum increased Lactobacillus abundance and reduced bacterial diversity and Enterobacteriaceae abundance compared with silage treated with molasses. Molasses addition reduced the relative concentration of structural carbohydrates (neutral and acid detergent fiber, and hemicellulose) after 30 days of ensiling. Finally, there was spoilage after 2 days and 4 days of aerobic exposure in C and LM silages respectively, whereas L silage had not spoiled after 4 days.

CONCLUSIONS

Although the combination of L. plantarum and molasses further optimized fermentation characteristics, L silage had better aerobic stability. © 2021 Society of Chemical Industry.

Effect of Different Kefir Source on Fermentation, Aerobic Stability, and Microbial Community of Alfalfa Silage

Simple Summary

Minimizing silage additives cost while increasing silage quality is important for a sustainable livestock enterprise, especially in undeveloped and developing countries. In this study, therefore, commercially available kefir yeast (CK) and homemade kefir culture (HK), as a low-cost additive, was applied at untreated a common control (CON) and three different application doses (5.0, 5.7, and 6.0 log cfu g⁻¹) on wilted alfalfa and evaluated with the fermentation characteristics and aerobic stability. The addition of HK with an application dose greater than 5.0 log cfu g⁻¹ prevents mold formation and inhibits yeast counts in silages. Indeed, both CK and HK improve the silage quality and aerobic stability of alfalfa even with low water-soluble carbohydrate content.

Abstract

The present study has been one of the first attempts to thoroughly examine the effects of different kefir sources on fermentation characteristics, aerobic stability, and microbial communities of alfalfa silages. The effects of commercial kefir (CK) and homemade kefir culture (HK) applied with untreated a common control (CON) and three different application doses (5.0, 5.7, and 6.0 log cfu g⁻¹) on wilted alfalfa and stored at an ambient temperature of 25–30 °C are studied. After 45 days of ensiling, fermentation characteristics and aerobic stability of silages were measured, and bacterial diversity was investigated by 16S ribosomal RNA gene sequencing using the GenomeLab™ GeXP platform. Both CK and HK accelerate more lactic acid production and reduced ammonia nitrogen concentration. Factor analysis of kefir sources suggests that the addition of kefir improves the aerobic stability of silages, even the initial water-soluble carbohydrate (WSC) content is inadequate via its antimicrobial effect on yeast and mold formation. Enterococcus faecium, Pediococcus pentosaceous and Lactobacillus brevis were dominant bacterial species among the treated groups at silo opening, while Lactobacillus plantarum and Lactobacillus brevis became dominant bacterial species after 7 days of aerobic exposure. In conclusion, the application of kefir on alfalfa silages improves fermentation quality and aerobic stability even with low WSC content.

Effects of Chopping Length and Additive on the Fermentation Quality and Aerobic Stability in Silage of Leymus chinensis

The objective of this experiment was to evaluate the effects of the chopping length and additive on the fermentation characteristics and aerobic stability in silage of Leymus chinensis. L. chinensis was chopped to 1–2 cm and 4–5 cm, and immediately ensiled with the three treatments, i.e., 2% sucrose (fresh weight basis; SU), 1 × 105 cfu/g Lactobacillus plantarum (LP) or 1 × 105 cfu/g LP plus 2% sucrose (SU+LP). Silage treated with distilled water served as the control. After silage processing for 30 and 90 d, the fermentation quality of L. chinensis silage was evaluated. The composition of the fermentation products and the pH value in the silage were determined at 1, 3, 5 and 7 d after opening the silo. The results showed that in L. chinensis silage there was a lower pH value, higher lactic acid content and better aerobic stability at the 1–2 cm length than those at the 4–5 cm (p < 0.001). When the chopping length was 4–5 cm, the addition of either LP or SU+LP increased the content of lactic acid and acetic acid, and decreased the pH value and butyric acid content, compared to those of the control and SU treatment (p < 0.001). Furthermore, combination treatment of SU+LP performed better than LP alone, and the aerobic stability time of L. chinensis silage at 4–5 cm without any additives was the worst. In conclusion, enhanced fermentation quality and aerobic stability can be obtained by processing L. chinensis silage with the shorter length. When the L. chinensis is cut longer, e.g., 4–5 cm in this study, LP or SU+LP could be used as an effective method to improve the fermentation quality and aerobic stability of L. chinensis silage.

Molecular typing tools for identifying and characterizing lactic acid bacteria: a review

Identification and classification of beneficial microbes is of the highest significance in food science and related industries. Conventional phenotypic approaches pose many challenges, and they may misidentify a target, limiting their use. Genotyping tools show comparatively better prospects, and they are widely used for distinguishing microorganisms. The techniques already employed in genotyping of lactic acid bacteria (LAB) are slightly different from one another, and each tool has its own advantages and disadvantages. This review paper compiles the comprehensive details of several fingerprinting tools that have been used for identifying and characterizing LAB at the species, sub-species, and strain levels. Notably, most of these approaches are based on restriction digestion, amplification using polymerase chain reaction, and sequencing. Nowadays, DNA sequencing technologies have made considerable progress in terms of cost, throughput, and methodology. A research journey to develop improved versions of generally applicable and economically viable tools for fingerprinting analysis is ongoing globally.

Analysis of the correlation between bacteria and fungi in sugarcane tops silage prior to and after aerobic exposure

The correlation between bacteria and fungi in sugarcane tops silage prior to and after aerobic exposure was analyzed. The results showed that the abundance of Lactobacillus increased from 0.03% to 27.84% from d 0-60. Additionally, the abundance of Pichia also increased from 0.003% to 15.46% from d 0-60. Following aerobic exposure, the abundance of Lactobacillus increased by 42.39% at d 3. Moreover, Pichia was the dominant fungal genus after aerobic exposure. Spearman's correlation analysis showed that Pichia was positively correlated with the genera Lactobacillus and Pediococcus, but negatively correlated with the genera Acinetobacter, Citrobacter, and Serratia. Aspergillus, Cladosporium, and Fusarium were positively correlated with the genera Clostridium, Lactobacillus, and Pediococcus, but negatively correlated with the genera Acinetobacter, Citrobacter, and Serratia. Spearman's correlation also suggested that Aspergillus, Cladosporium, and Fusarium could be inhibited by screening Serratia, thereby reducing mycotoxins in silage.

Dynamics of microbial community during ensiling direct-cut alfalfa with and without LAB inoculant and sugar

AIM

To gain deeper insights into the clostridial community dynamics and chemical transformations during the ensiling of alfalfa.

METHODS AND RESULTS

Direct-cut alfalfa silage (with the dry matter content of 240 g kg^-1 ) was prepared with or without the addition of a lactic acid bacterial inoculant and sucrose. Silages were sampled at 0, 3, 7, 14, 28 and 56 days after ensiling and their bacterial community was determined using high-throughput sequencing with a special focus on the clostridial community. A clostridial fermentation occurred in the control silage, with high contents of acetic acid, butyric acid and ammonia nitrogen and Clostridia counts; while the inoculated silage was well preserved, with low pH and high lactic acid content. Lactic acid bacteria dominated the bacterial community during the ensiling process. In the control silage, Weissella confusa, Lactobacillus brevis, Enterococcus mundtii and Pediococcus acidilactici were identified at the beginning of the fermentation. Thereafter, W. confusa, Lactobacillus helsingborgensis and Bifidobacterium asteroides appeared and quickly prevailed. In the inoculated silage, Lactobacillus plantarum dominated the whole ensiling process. The genus Clostridium dominated the clostridial community, and was depressed with the inoculated treatment. Clostridium perfringens, Garciella sp. and Clostridium baratii were the main initiators of the clostridial fermentation of the control silage, while Clostridium tyrobutyricum became the most abundant Clostridia with prolonged ensiling. Overall in the inoculated silage, little changes in the clostridial community were observed throughout the ensiling period. Treating alfalfa silage with a homolactic acid-based bacterial inoculant prevented a clostridial fermentation resulting in more efficient fermentation.

CONCLUSION

Distinct changes in the bacterial community with a special focus on the clostridial community were associated with the development of the clostridial fermentation during the ensiling of alfalfa.

SIGNIFICANCE AND IMPACT OF THE STUDY

High-throughput sequencing based on a novel Clostridia-specific primer set proved a potentially useful tool to study the clostridial community dynamics, and could aid to elucidate the mechanism by which the clostridial fermentation develops during the ensiling of alfalfa.

Diversity of lactic acid bacteria in vegetable-based and meat-based fermented foods produced in the central region of Vietnam

The diversity of lactic acid bacteria (LAB) in naturally fermented foods produced in Hue, a city in the central region of Vietnam, was examined. From local markets, a total of 25 samples of three vegetable-based fermented products, specifically dua gia (bean sprouts), dua cai (cabbage), and mang chua (bamboo shoots), and two meat-based fermented products, specifically nem chua (uncooked pork) and tre (cooked pork) were obtained. The LAB diversity was assessed by quantitative real-time polymerase chain reaction (PCR) and qualitative denaturing gradient gel electrophoresis. Lactic and acetic acid contents were greater in meat-based products than in vegetable-based products. Major LAB species found in vegetable-based products (Lactobacillus plantarum, Lactobacillus fermentum, and Lactobacillus helveticus) were different from those identified in meat-based products (Pediococcus pentosaceus, Weissella cibaria, and Lactococcus lactis). The total bacterial population was approximately 10^9-10 copies/g regardless of the food item, with the proportion of Lactobacillus spp. determined to be from 78% (dua cai) to 94% (nem chua).