Bacillus cereus liquid fertilizer was produced from Agaricus bisporus industrial wastewater

Analysis of surfactant production by Bacillus cereus GX7 and optimization of fermentation conditions

Although biosurfactants have many advantages compared to chemical surfactants, biosurfactants are still limited by problems such as low yields and high production costs. In the present study, a strain of Bacillus Cereus (GX7) isolated from an oil tank bottom sludge of Shengli Oil Field (China) was selected as a highly effective surfactant producer. The biosurfactant produced by GX7 was extracted, purified, and analyzed by TLC, FT-IR, and LC-MS/MS. The results showed that the biosurfactant was surfactin of lipopeptide surfactant. Single-factor experiments were used to optimize the fermentation process of the strain from two aspects: the composition of the fermentation medium (carbon source, nitrogen source) and the fermentation conditions (temperature, pH, inoculation amount, rotation speed, and fermentation time). The surface tension and emulsification index of the fermentation broth were used to evaluate the optimal fermentation conditions. The results showed that the best carbon and nitrogen sources were glucose and peptone, and the optimum temperature, inoculum amount, pH, rotation speed, and fermentation time were 30 ℃, 1%, 7.5, 150 rpm, and 48 h, respectively. After optimization, the surface tension and emulsification index of fermentation broth were 26.84 mN/m and 57.84%, respectively. Moreover, the results also prove that the biosurfactant produced by this strain has good stability in a wide range of temperature, pH, and salt concentration.

Recovery and utilization of waste filtrate from industrial biological fermentation: Development and metabolite profile of the Bacillus cereus liquid bio-fertilizer

Most fermentation waste filtrates can be used as raw materials for producing bio-fertilizers to reduce wastewater emissions and environmental pollution, but their bio-fertilizer utilization depends on the nutrients contained and their metabolized by functional microorganism. To achieve bio-fertilizer utilization of Acremonium terricola fermented waste filtrate, this study systematically explored the functional microbial species for making good use of waste liquid, optimized material process parameters for bio-fertilizer production based on D-optimal mixture design method, and analyzed the composition of the waste filtrate and its metabolism by functional microorganisms using a non-targeted LC-MS metagenomics technique. The results showed that Bacillus cereus was the functional microbial candidate for producing bio-fertilizer because of its more efficiently utilize the waste filtrate than other Bacillus sp. The optimal material process parameters of the liquid bio-fertilizer were the inoculum dose of 5% (v:v, %), 80% of waste filtrate, 0.25% of N, 3.5% of P2O5, 3.25% of K2O of mass percentage. Under these conditions, the colony forming unit (CFU) of Bacillus cereus could reach (1.59 ± 0.01) × 108 CFU/mL, which met the bio-fertilizer standard requirements of the People's Republic of China (NY/T798). Furthermore, the potential functions of bio-fertilizer were studied based on comparison of raw materials and production components: on the one hand, waste filtrate contained abundant of nitrogen and carbon sources, and bioactive substances secreted by Acremonium terricola, such as β-alanyl-L-lysine, anserine, UMP, L-lactic acid and etc., which could meet the nutrient requirements of the growth of Bacillus cereus; On the other hand, some compounds of waste filtrate with the potential to benefit the plant growth and defense, such as betaine aldehyde, (2E,6E)-farnesol, homogentisic acid and etc., were significantly up regulated by Bacillus cereus utilization of the filtrate. To sum up, this work highlighted that the waste filtrate could be efficiently developed into liquid bio-fertilizer by Bacillus cereus.

Improved production of andrimid in Erwinia persicina BST187 strain by fermentation optimization

BACKGROUND

Andrimid is reported to be a novel kind of polyketide-nonribosomal peptide hybrid product (PK-NRPs) that inhibits fatty acid biosynthesis in bacteria. Considering its great potential in biomedicine and biofarming, intensive studies have been conducted to increase the production of andrimid to overcome the excessive costs of chemosynthesis. In screening for species with broad-spectrum antibacterial activity, we detected andrimid in the fermentation products of Erwinia persicina BST187. To increase andrimid production, the BST187 fermentation medium formulation and fermentation conditions were optimized by using systematic design of experiments (One-Factor-At-A-Time, Plackett-Burman design, Response Surface Methodology).

RESULTS

The results indicate that the actual andrimid production reached 140.3 ± 1.28 mg/L under the optimized conditions (trisodium citrate dihydrate-30 g/L, beef extract-17.1 g/L, MgCl2·6H2O-100 mM, inoculation amount-1%, initial pH-7.0, fermentation time-36 h, temperature-19.7℃), which is 20-fold greater than the initial condition without optimization (7.00 ± 0.40 mg/L), consistent with the improved antibacterial effect of the fermentation supernatant.

CONCLUSIONS

The present study provides valuable information for improving andrimid production via optimization of the fermentation process, which will be of great value in the future industrialization of andrimid production.

Combining Cell-Free Expression and Multifactor Optimization for Enhanced Biosynthesis of Cinnamyl Alcohol

Cell-free expression systems have emerged as a potent and promising platform for the biosynthesis of chemicals by reconstituting in vitro expressed enzymes. Here, we report cell-free biosynthesis of cinnamyl alcohol (cinOH) with enhanced productivity by using the Plackett-Burman experimental design for multifactor optimization. Initially, four enzymes were individually expressed in vitro and directly mixed to reconstitute a biosynthetic route for the synthesis of cinOH. Then, the Plackett-Burman experimental design was used to screen multiple reaction factors and found three crucial parameters (i.e., reaction temperature, reaction volume, and carboxylic acid reductase) for the cinOH production. With the optimum reaction conditions, approximately 300 μM of cinOH was synthesized after 10 h of cell-free biosynthesis. Extending the production time to 24 h also increased the production to a maximum yield of 807 μM, which is nearly 10 times higher than the initial yield without optimization. This study demonstrates that cell-free biosynthesis can be combined with other powerful optimization methodologies such as the Plackett-Burman experimental design for enhanced production of valuable chemicals.

Fermentation of Agaricus bisporus for antioxidant activity: response surface optimization, chemical components, and mechanism

Agaricus bisporus is one of the most widely cultivated edible mushrooms in the world. The chemical components of A. bisporus have a wide range of biological activities. In order to deeply understand the antioxidant properties of A. bisporus, this study conducted an investigation on the components of A. bisporus fermentation. Through the single factor experiment and response surface optimization, it was found that when the C/N ratio was 45:1, the inoculum concentration was 10%, and the fermentation time was 7 d, the n-butanol extract of the fermentation product had the strongest scavenging capacity for free radical generated through 2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS·⁺). The concentration for 50% of the maximal effect (EC₅₀) was 0.33 ± 0.01 mg/mL. Moreover, in order to identify the two main components, the elution-extrusion counter-current chromatography (EECCC) was employed for separation, where 5,5'-oxy-dimethyl-bis(2-furfuraldehyde) and 5-(butoxymethyl) furfural were obtained. The antioxidant activity of 5,5'-oxy-dimethyl-bis(2-furfuraldehyde) (EC₅₀ = 0.26 ± 0.01 mg/mL) was superior to that of 5-butylmethyl furfural (EC₅₀ = 1.52 ± 0.02 mg/mL), indicating that 5,5'-oxy-dimethyl-bis(2-furfuraldehyde) was the main antioxidant in the fermentation products. The thermodynamic parameters and frontier molecular orbitals of 5,5'-oxy-dimethyl-bis (2-furanaldehyde) was evaluated by density functional theory (DFT). The result indicated 5,5'-oxy-dimethyl-bis(2-furanaldehyde) scavenged free radicals in polar media through single electron transfer followed by proton transfer (SET-PT).

An Insight into Microbial Inoculants for Bioconversion of Waste Biomass into Sustainable "Bio-Organic" Fertilizers: A Bibliometric Analysis and Systematic Literature Review

The plant-microbe holobiont has garnered considerable attention in recent years, highlighting its importance as an ecological unit. Similarly, manipulation of the microbial entities involved in the rhizospheric microbiome for sustainable agriculture has also been in the limelight, generating several commercial bioformulations to enhance crop yield and pest resistance. These bioformulations were termed biofertilizers, with the consistent existence and evolution of different types. However, an emerging area of interest has recently focused on the application of these microorganisms for waste valorization and the production of "bio-organic" fertilizers as a result. In this study, we performed a bibliometric analysis and systematic review of the literature retrieved from Scopus and Web of Science to determine the type of microbial inoculants used for the bioconversion of waste into "bio-organic" fertilizers. The Bacillus, Acidothiobacillus species, cyanobacterial biomass species, Aspergillus sp. and Trichoderma sp. were identified to be consistently used for the recovery of nutrients and bioconversion of wastes used for the promotion of plant growth. Cyanobacterial strains were used predominantly for wastewater treatment, while Bacillus, Acidothiobacillus, and Aspergillus were used on a wide variety of wastes such as sawdust, agricultural waste, poultry bone meal, crustacean shell waste, food waste, and wastewater treatment plant (WWTP) sewage sludge ash. Several bioconversion strategies were observed such as submerged fermentation, solid-state fermentation, aerobic composting, granulation with microbiological activation, and biodegradation. Diverse groups of microorganisms (bacteria and fungi) with different enzymatic functionalities such as chitinolysis, lignocellulolytic, and proteolysis, in addition to their plant growth promoting properties being explored as a consortium for application as an inoculum waste bioconversion to fertilizers. Combining the efficiency of such functional and compatible microbial species for efficient bioconversion as well as higher plant growth and crop yield is an enticing opportunity for "bio-organic" fertilizer research.

Endophyte colonization enhanced cadmium phytoremediation by improving endosphere and rhizosphere microecology characteristics

This study investigated the phytoremediation efficiency of Cd-contaminated soils by hyperaccumulator P. acinosa and its endophyte B. cereus, and evaluated the variation of rhizosphere/endosphere microecology characteristics. The result showed that endophyte PE31, which could successfully colonize on P. acinosa root, increased plant Cd uptake by 42.90% and 28.85% in low and high Cd contaminated soils by promotion of plant biomass and Cd concentration in plant tissues. The improved phytoremediation may attribute to the endophyte inoculation, which significantly improved the bioavailable heavy metal (HM) percentage, nutrient cycling related enzyme activities and nutrient contents including available potassium, phosphorus and organic matter. Additionally, the relative abundance beneficial bacteria Bacillus (significantly increased by 81.23% and 34.03% in the endosphere, and by 4.86% and 8.54% in rhizosphere in low and high Cd contaminated soils) and Lysobacter, showed positive and close correlation with plant growth and HM accumulation. These results indicated that endophyte inoculation could reshape rhizosphere and endosphere microecology characteristics, which enhanced the potential for phytoremediation of Cd contaminated soils.

Increase of P and Cd bioavailability in the rhizosphere by endophytes promoted phytoremediation efficiency of Phytolacca acinosa

The information about the spatial distribution of bioavailable phosphorus (P) and heavy metal (HM) in the rhizosphere could aid in the precise phytoremediation regulation. In this study, a rhizobox system was adapted to study soil-root interactions and used to access the endophyte inoculation variation on bioavailable P and cadmium (Cd) spatial distribution during phytoremediation of Cd contaminated soils. Results showed that endophyte PE31 Bacillus cereus inoculation enhanced Cd uptake of P. acinosa by 52.70% and 46.73% in low and high Cd contaminated soils, increasing the phytoremediation hotspot area from 45.78% and 15.29% to 60.97% and 21.80%, respectively. Available P and Cd significantly diminished because root activities depleted large amounts of bioavailable P and Cd concentrations. However, PE31 increased bioavailable P and Cd concentration in the rhizosphere soil. The bioavailable P enhancement in the rhizosphere was positively correlated to plant growth and Cd accumulation. Overall, endophyte inoculation compensated the diminution of bioavailable P and Cd in the rhizosphere to improve plant biomass and HM absorption, and thus promote phytoremediation efficiency. This study helped to better understand bioavailable P and Cd spatial distribution under endophyte inoculation, which could provide effective management strategies for the precise regulation of phytoremediation.

Effects of biofertilizer on soil microbial diversity and antibiotic resistance genes

Spread of antibiotic resistance or the presence of antibiotic resistance genes (ARGs) in pathogens is a globally recognized threat to human health. Numerous studies have shown that application of organic fertilizers may increase the risk of ARGs, however, the risk of resistance genes associated with biofertilizers is largely unknown. To investigate whether biofertilizer application introduces ARGs to the soil, we used high-throughput quantitative polymerization chain reaction (HT-qPCR) to explore the effect of biofertilizer application over three years on soil ARGs in three orchards with different locations in China. Redundancy analysis showed specific and significant differences in the beta diversity of soil bacteria and fungi between treatments (fertilizer vs. no fertilizer). One-way ANOVA analysis revealed findings of the main driver of the significant difference in microbial community structure between fertilizer and control treatment was the change in soil properties following the application of biofertilizer. A total of 139 ARGs and 27 MGEs (mobile genetic elements), and 46 ARGs and 6 MGEs from 11 major taxa were detected in biofertilizer and soil samples, respectively. Only the samples from Guangxi had significant differences in the detected number of ARGs and MGEs between fertilization and control. Through structural equation modeling (SEM), we found that soil properties indirectly affected ARGs by shaping bacterial diversity, while bacterial abundance directly affected ARGs. Biofertilizer application did not significantly alter the relative abundance of ARGs in soil due to the complexity of the soil environment and competition between exogenous and native microorganisms. This study provided new insights into the spread of the antibiotic resistome of the soil through biofertilizer applications.