Project description:To better understand the mechanism underlying the citric acid (CA)-regulated silage fermentation, we investigated the bacterial community and fermentation quality of king grass (KG) ensiled without (CK) or with Lactobacillus plantarum (L), CA and the combination of L and CA (CAL). The bacterial community was characterized by using the 16Sr DNA sequencing technology. The L and CA treatments altered the silage bacterial community of KG, showing reduced bacterial diversity, while the abundance of desirable genus Lactobacillus was increased, and the abundances of undesirable genus Dysgonomonas and Pseudomonas were decreased. The additives also significantly raised the lactic acid content, dropped the pH, and reduced the contents of acetic acid, propionic acid, and ammonia-N in ensiled KG (P < 0.01). Besides, the combination treatment was more effective on silage fermentation with the highest pH and lactic acid content, while the contents of acetic acid, propionic acid, and ammonia-N were the lowest (P < 0.01). Moreover, CAL treatment exerted a notable influence on the bacterial community, with the lowest operational taxonomic unit (OTU) number and highest abundance of Lactobacillus. Furthermore, the bacterial community was significantly correlated with fermentation characteristics. These results proved that L and CA enhanced the KG silage quality, and the combination had a beneficial synergistic effect.
Project description:ObjectiveThis study aimed to investigate the promoting effect of a Bacillus velezensis (BV) strain on lactic acid bacteria (LAB) and determine its influence on the fermentation quality and aerobic stability of silage.MethodsFlat colony counting method was used to evaluate the effect of BV on the growth of LAB. Freshly harvested whole-plant corn was inoculated separately with BV and L. plantarum (LP), along with an uninoculated control group (CK), and assessed at 1, 3, 5, 7, 15, and 30 days of ensiling.ResultsThe results indicated that BV exhibited a proliferative effect on Weissella confusa, Lactobacillus plantarum L-2, and Pediococcus pentosaceus. And exhibited a more rapid pH reduction in BV-inoculated silage compared with that in CK and LP-inoculated silage during the initial stage of ensiling. Throughout ensiling, the BV and LP experimental groups showed enhanced silage fermentation quality over CK. Additionally, relative to LP-inoculated silage, BV-inoculated silage displayed reduced pH and propionic acid. BV also prolonged aerobic stability under aerobic conditions. The microbial community in BV-inoculated silage showed greater stability than that in LP-inoculated silage. Additionally, Firmicutes and Lactobacillus exhibited more rapid elevation initially in BV versus LP-inoculated silage, but reached comparable levels between the two inoculation groups in the later stage.ConclusionIn summary, BV enhanced the efficacy and aerobic stability of whole-plant corn silage fermentation by stimulating LAB proliferation.
Project description:Meloidogyne incognita is obligate parasitic nematode with a wide variety of hosts that causes huge economic losses every year. In an effort to identify novel bacterial biocontrols against M. incognita, the nematicidal activity of Bacillus velezensis strain Bv-25 obtained from cucumber rhizosphere soil was measured. Strain Bv-25 could inhibit the egg hatching of M. incognita and had strong nematicidal activity, with the mortality rate of second-stage M. incognita juveniles (J2s) at 100% within 12 h of exposure to Bv-25 fermentation broth. The M. incognita genes ord-1, mpk-1, and flp-18 were suppressed by Bv-25 fumigation treatment after 48 h. Strain Bv-25 could colonize cucumber roots, with 5.94 × 107 colony-forming units/g attached within 24 h, effectively reducing the infection rate with J2s by 98.6%. The bacteria up-regulated the expression levels of cucumber defense response genes pr1, pr3, and lox1 and induced resistance to M. incognita in split-root trials. Potted trials showed that Bv-25 reduced cucumber root knots by 73.8%. The field experiment demonstrated that disease index was reduced by 61.6%, cucumber height increased by 14.4%, and yield increased by 36.5% in Bv-25-treated plants compared with control. To summarize, B. velezensis strain Bv-25 strain has good potential to control root-knot nematodes both when colonizing the plant roots and through its volatile compounds.
Project description:In order to better understand the effect of wilting treatment on silage, we study analyzed the fermentation quality of unwilted (CK) and wilted (WT) king grass silage, and the dynamic changes of microorganisms in silage and aerobic exposure. After 30 days of silage, WT silage significantly reduced the pH of the silage (p < 0.05) and increased the contents of lactic acid and acetic acid (p < 0.05), but did not reduce the content of Ammonia-N (p > 0.05). Wilting treatment increased bacterial and fungal diversity during silage but decreased fungal diversity during aerobic exposure. The relative abundance of Lactococcus and Enterococcus in wilting silage increased. In the aerobic exposure stage, the relative abundance of Klebsiella decreased, but the relative abundance of Enterobacter increased in wilting treatment silage. In addition, the relative abundance of Acinetobacter and Ignatzschineria increased after 5 days of aerobic exposure. In contrast with unwilted silage, wilting treatment silage after aerobic exposure had no Candida, but the relative abundance of Wickerhamomyces increased. The results showed that wilting treatment could raise the silage quality of king grass. However, WT silage did not inhibit the reproduction of harmful microorganisms during aerobic exposure and did not significantly improve the aerobic stability of silage.
Project description:The objective of this study was to assess the effect of harvesting time on the fermentation characteristics, chemical composition, and microbial community of king grass silage. King grass was harvested at three growth periods of 90 days (KN90S), 110 days (KN110S), and 130 days (KN130S); chopped into 2-3-cm particle size; and ensiled in polyethylene bags (20 × 30 cm). The fermentation quality and chemical composition of silages were analyzed after 1, 3, 7, 14, 30, and 60 days of ensiling. Bacterial community of silage ensiled for 60 days was profiled using next generation sequencing (NGS) technology. The KN110S showed the most extensive lactic acid (LA) fermentation during 7 days of fermentation compared to KN90S and KN130S. After 60 days of fermentation, the KN110S showed the lowest pH and the highest lactic acid content among the three treatments. The butyric acid and ammonia nitrogen contents of KN90S and KN130S were significantly greater than those of KN110S (p < 0.05). After a timespan of 60 days of ensiling, the bacterial community of king grass silage was predominantly populated by Proteobacteria in phylum level, whereas unclassified Enterobacteriaceae genus remained dominant in all silages. A higher relative abundance of Clostridium was observed in KN90S and KN130S, but not in KN110S, and greater abundance of Lactococcus appeared in KN110S and KN130S silages than KN90S. It is concluded that harvesting time had an important effect on the fermentation quality and microbial community of king grass silage.
Project description:This study was designed to evaluate the potential of bioflocculant producing strains isolated from wastewater sludge. According to the Plackett-Burman design, the response surface revealed glucose, magnesium sulfate, and ammonium sulfate as critical media components of the nutritional source, whereas the central composite design affirmed an optimum concentration of the critical nutritional source as 16.0 g/l (glucose), 3.5 g/l magnesium sulfate heptahydrate (MgSO4.7H2O), and 1.6 g/l ammonium sulfate ( (NH4)2SO4), yielding an optimal flocculation activity of 96.8%. Fourier Transformer Infrared Spectroscopy (FTIR) analysis confirmed the presence of hydroxyl, carboxyl and methoxyl in the structure of the bioflocculant. Additionally, chemical analysis affirmed the presence of mainly a polysaccharide in the main backbone of the purified bioflocculant with no detection of protein. Energy Dispersive X-ray analysis affirmed the presence of chlorine, phosphorous, oxygen and chlorine as representatives of elemental composition. Thermogravimetric (TGA) analysis revealed over 60% weight was retained at a temperature range of 700 °C. The purified bioflocculant remarkably removed chemical oxygen demand, biological oxygen demand and turbidity in brewery wastewater. This study suggested that the bioflocculant might be an alternate candidate for wastewater treatment.
Project description:Plant growth-promoting rhizobacteria (PGPR) have been reported to influence plant growth, yield, and nutrient uptake by an array of mechanisms. Uncovering the behavioral dynamics of PGPR is one of the most important issues necessary for understanding their functional performances. In this study, strain NJAU-Z9 which was found to possess complex functions and efficient rhizospheric colonization ability was selected from plenty of bacterial strains isolated randomly from the pepper rhizosphere soil and identified as Bacillus velezensis. Repeated seedling nursing tests performed absolute growth-promoting advantage for the novel isolated strain. After that, primers for the quantitative detection were designed based on its whole genome sequence (WGS), and a real-time PCR method was utilized to explore strategies for monitoring the strain in natural soil and in the pepper rhizosphere. Results showed based on the whole genome, two primers were identified as NJAU-Z9-specific quantitative PCR primers. Two seasonal pot experiments demonstrated that strain NJAU-Z9 effectively colonized the rhizosphere measured by the novel abundance detecting strategy, improved plant growth, and showed a positive correlation between bacterial number and biomass. This study offers a strategy based on a real-time PCR method for directly monitoring B. velezensis strain NJAU-Z9 in the soil and the rhizosphere and provides a reference for the quantitative study of other PGPR strains based on WGSs.