Microbial synthesis of poly-γ-glutamic acid (γ-PGA) with fulvic acid powder, the waste from yeast molasses fermentation

Effective Decolorization of Poly-γ-Glutamic Acid Fermentation Broth by Integrated Activated Carbon Adsorption and Isoelectric Point Precipitation of Glutamic Acid

Poly-γ-glutamic acid (γ-PGA) is widely used in the field of biomedicine, food, agriculture, and ecological remediation. For the biosynthesis of γ-PGA, the pigments and remaining glutamate are two big problems that impede γ-PGA production by fermentation, and a trade-off between the decolorization rate and γ-PGA recovery rate during the purification process was found. The optimized static activated carbon adsorption conditions for treating the 2-times diluted cell-free supernatant (i.e., feed solution) was as follows: 0.51% 200-mesh, 1000 iodine value, coal-based activated carbon, pH 6.0, 140 min, and 40 °C. Under the optimized conditions, the decolorization rate reached 94.42%, and the recovery rate of γ-PGA was 94.22%. During the adsorption process, the pigments were adsorbed on the activated carbon surface in a monolayer, and the process was a spontaneous, heat-absorbing, and entropy-increasing process. Then, the decolorization flow rate optimized for the dynamic decolorization experiment was 1 BV/h. However, the remaining glutamate was still a problem after the activated carbon adsorption. After isoelectric point (IEP) precipitation of glutamic acid, the glutamic acid can be recovered, and the residual pigment can be further removed. Finally, an integrated decolorization process of activated carbon adsorption and IEP precipitation of glutamic acid was developed. After the integrated process, the decolorization and glutamic acid precipitation rates were 95.80% and 49.02%, respectively. The recovered glutamic acid can be reused in the next fermentation process.

Screening and effects of intestinal probiotics on growth performance, gut health, immunity, and disease resistance of Nile tilapia (Oreochromis niloticus) against Streptococcus agalactiae

In the present study, 59 autochthonous bacteria were isolated from the intestine of tilapia. Following enzyme producing activity, antagonistic ability, hemolytic activity, drug sensitivity assessments, and in vivo safety evaluation, 7 potential probiotic strains were screened out: Bacillus tequilensis BT0825-2 (BT), Bacillus aryabhattai BA0829-3 (BA1), Bacillus megaterium BM0505-6 (BM), Bacillus velezensis BV0505-11 (BV), Bacillus licheniformis BL0505-18 (BL), B. aryabhattai BA0505-19 (BA2), and Lactococcus lactis LL0306-15 (LL). Subsequently, tilapia were fed basal diets (CT) and basal diets supplemented with 108 CFU/g of BT, BA1, BM, BV, BL, BA2 and LL, respectively. After 56 days of continuous feeding, the growth parameters (weight gain, final weight, and specific growth rate) showed significant improvement (p < 0.05) in both BM and BA2 groups. The total cholesterol and triglycerides of serum were significantly decreased in BV and LL groups (p < 0.05). The superoxide dismutase, glutathione reductase, and lysozyme of BV, BA2 and LL groups were increased, and the malondialdehyde of BV group was significantly decreased. The villous height and amylase of midgut were increased in BV, BA2 and LL groups. In addition, the expression levels of ZO-1 and occludin genes in the midgut of tilapia were enhanced in BM, BV, BA2 and LL groups. The supplementation of probiotics reduced the abundance of Cyanobacteria and increased the abundance of Actinobacteria at the phylum level. At the genus level, the addition of probiotics increased the abundance of Romboutsia. Furthermore, improvement in the expression of immune-related genes were observed, including interleukin 1β, interleukin 10, tumor necrosis factor alpha, and transforming growth factor beta (p < 0.05). After challenging with S. agalactiae, the survival rates of BV, BA2 and LL groups were significantly higher than CT group (p < 0.05). Above results indicated that BM, BA2, BV and LL improved growth performance, gut health or immunity of tilapia, which can be applied in tilapia aquaculture.

Synthesis of Poly-γ-Glutamic Acid and Its Application in Biomedical Materials

Poly-γ-glutamic acid (γ-PGA) is a natural polymer composed of glutamic acid monomer and it has garnered substantial attention in both the fields of material science and biomedicine. Its remarkable cell compatibility, degradability, and other advantageous characteristics have made it a vital component in the medical field. In this comprehensive review, we delve into the production methods, primary application forms, and medical applications of γ-PGA, drawing from numerous prior studies. Among the four production methods for PGA, microbial fermentation currently stands as the most widely employed. This method has seen various optimization strategies, which we summarize here. From drug delivery systems to tissue engineering and wound healing, γ-PGA's versatility and unique properties have facilitated its successful integration into diverse medical applications, underlining its potential to enhance healthcare outcomes. The objective of this review is to establish a foundational knowledge base for further research in this field.

Cooperative Action of Fulvic Acid and Bacillus paralicheniformis Ferment in Regulating Soil Microbiota and Improving Soil Fertility and Plant Resistance to Bacterial Wilt Disease

Excessive continuous cropping and soil degradation, such as acidification, hardening, fertility decline, and the degradation of microbial community, lead to the epidemic of soilborne diseases and cause great loss in agriculture production. Application of fulvic acid can improve the growth and yield of various crops and effectively suppress soilborne plant diseases. Bacillus paralicheniformis strain 285-3 producing poly-gamma-glutamic acid is used to remove the organic acid that can cause soil acidification and increase the fertilizer effect of fulvic acid and the effect of improving soil quality and inhibiting soilborne disease. In field experiments, the application of fulvic acid and Bacillus paralicheniformis ferment effectively reduced the incidence of bacterial wilt disease and improved soil fertility. Both fulvic acid powder and B. paralicheniformis ferment improved soil microbial diversity and increased the complexity and stability of the microbial network. For B. paralicheniformis ferment, the molecular weight of poly-gamma-glutamic acid became smaller after heating, which could better improve the soil microbial community and network structure. In fulvic acid and B. paralicheniformis ferment-treated soils, the synergistic interaction between microorganisms increased and the number of keystone microorganisms increased, which included antagonistic bacteria and plant growth-promoting bacteria. Changes in the microbial community and network structure were the main reason for the reduced incidence of bacterial wilt disease. Application of fulvic acid and Bacillus paralicheniformis ferment improved soil physicochemical properties and effectively controlled bacterial wilt disease by changing microbial community and network structure and enriching antagonistic and beneficial bacteria. IMPORTANCE Continuous cropping tobacco has led to soil degradation and caused soilborne bacterial wilt disease. Fulvic acid as a biostimulator was applied to restore soil and control bacterial wilt disease. For improving its effect, fulvic acid was fermented with Bacillus paralicheniformis strain 285-3 producing poly-gamma-glutamic acid. Fulvic acid and B. paralicheniformis ferment inhibited bacterial wilt disease, improved soil quality, enriched beneficial bacteria, and increased microbial diversity and microbial network complexity. Some keystone microorganisms in fulvic acid and B. paralicheniformis ferment-treated soils had potential antimicrobial activity and plant growth-promoting attributes. Fulvic acid and B. paralicheniformis 285-3 ferment could be used to restore soil quality and microbiota and control bacterial wilt disease. This study found new biomaterial to control soilborne bacterial disease by combining fulvic acid and poly-gamma-glutamic acid application.

Removal of humic acid interference in soil enzymatic analysis using poly-γ-glutamic acid

Soil enzymes are biological indicators in environmental and agricultural monitoring. However, brownish humic acid (HA) in samples interferes significantly with various analytical methods, especially in optical-based techniques. Here, we implemented a coagulation-flocculation process to carry out continuously an enzymatic reaction without separation and transfer of a sample solution. The elimination of HA in a soil suspension using poly-γ-glutamic acid (PGA) by coagulation to minimize the HA interference in soil enzymatic analysis was investigated. As a result of the optimization of preliminary parameters, the removal efficiency of HA was > 92% in 100 mg L^-1 HA in neutral pH, using 100 mg L^-1 PGA and aluminum trivalent as a coagulant aid. However, the fluorescent intensity of the enzyme product (i.e., 4-methylumbelliferone) decreases by about 50% as HA was removed under the conditions used. A decrease in the enzymatic detection of 3,3',5,5'-tetramethylbenzidine (TMB) was not observed from treated samples even though the initial level of HA was different. The results suggested that the coagulation-flocculation approach is suitable for the reduction of HA interference, while maintaining target analyte detection. Therefore, the proposed sample treatment can be used to examine enzyme activity based on TMB product detection without regular standard addition calibration.

Efficient molasses utilization for low-molecular-weight poly-γ-glutamic acid production using a novel Bacillus subtilis stain

Background

Poly-γ-glutamic acid (γ-PGA) is a biopolymer and has various applications based on its biocompatibility, non-toxicity, and edibility. Low-molecular-weight (Mw)-γ-PGA has promising applications in agriculture and pharmaceuticals. It is traditionally produced by enzymatic hydrolysis. Cost-effective bioproduction of low-Mw-γ-PGA is essential for commercial application of γ-PGA.

Results

Bacillus subtilis 242 is a newly isolated low-Mw-γ-PGA-producing strain. To develop cost-effective production of γ-PGA using this newly isolated strain, cane molasses and corn steep liquor were used to produce γ-PGA. The concentration of cane molasses was optimized and 100 g/L cane molasses resulted in high γ-PGA production. The effects of yeast extract and corn steep liquor on γ-PGA yield were investigated. High concentration of γ-PGA was obtained in the medium with corn steep liquor. A concentration of 32.14 g/L γ-PGA was achieved in fed-batch fermentation, with a productivity of 0.67 g/L/h and a percentage yield (g_γ-PGA/g_glutamate) of 106.39%. The Mw of γ-PGA was 27.99 kDa.

Conclusion

This study demonstrated the potential application of B. subtilis 242 for cost-effective production of low-Mw-γ-PGA from cane molasses.