Screening and optimization of nutritional factors for higher dextransucrase production by Leuconostocmesenteroides NRRL B-640 using statistical approach

Screening, and Optimization of Fermentation Medium to Produce Secondary Metabolites from Bacillus amyloliquefaciens, for the Biocontrol of Early Leaf Spot Disease, and Growth Promoting Effects on Peanut (Arachis hypogaea L.)

A novel Bacillus amyloliquefaciens BAM strain, with novel fermentation nutrient mediums and compositions, could produce potent antifungal secondary metabolites, as the existing strains face resistance from fungus pathogens. In the current study, we introduced two novel nutrient mediums for the fermentation process, semolina and peanut root extract, as carbon and nitrogen sources in order to maximize the antifungal effects of B. amyloliquefaciens against Cercaspora arachidichola to control early leaf spot disease in peanuts. Based on a single-factor test and the central composite design of response surface methodology, the optimum fermentation medium for Bacillus amyloliquefaciens antagonistic substance was determined, containing 15 gm/L of semolina flour, 12.5 gm/L of beef extract, and 0.5 gm/L of magnesium sulfate, which inhibited the fungal growth by 91%. In vitro, antagonistic activity showed that the fermentation broth of B. amyloliquefaciens BAM with the optimized medium formulation had an inhibition rate of (92.62 ± 2.07)% on the growth of C. arachidichola. Disease control effects in pot experiments show that the pre-infection spray of B. amyloliquefaciens BAM broth had significant efficiency of (92.00 ± 3.79)% in comparison to post-infection spray. B. amyloliquefaciens BAM broth significantly promoted peanut plant growth and physiological parameters and reduced the biotic stress of C. archidechola. Studies revealed that B. amyloliquefaciens BAM with a novel fermentation formulation could be an ideal biocontrol and biofertilizer agent and help in early disease management of early leaf spots in peanuts.

Indole-3-acetic acid production by Streptomyces fradiae NKZ-259 and its formulation to enhance plant growth

BACKGROUND

Indole-3-acetic acid (IAA) is produced by microorganisms and plants via either tryptophan-dependent or tryptophan-independent pathways. Herein, we investigated the optimisation of IAA production by Streptomyces fradiae NKZ-259 and its formulation as a plant growth promoter to improve economic and agricultural development.

RESULTS

The maximum IAA yield achieved using optimal conditions was 82.363 μg/mL in the presence of 2 g/L tryptophan after 6 days of incubation. Thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) analysis of putative IAA revealed an RF value of 0.69 and a retention time of 11.842 min, comparable with the IAA standard. Regarding product formulation, kaolin-based powder achieved a suspension rate of 73.74% and a wetting time of 80 s. This carrier exhibited good shelf life stability for NKZ-259, and the cell population did not decrease obviously over 4 months of storage at 4 °C. In vivo analysis of plant growth promotion showed that tomato seedlings treated with kaolin powder containing NKZ-259 cells displayed a significant increase in root and shoot length of 7.97 cm and 32.77 cm, respectively, and an increase in fresh weight and dry weight of 6.72 g and 1.34 g. Compared to controls, plant growth parameters were increased almost it two-fold.

CONCLUSION

Optimising the culture conditions resulted in an almost four-fold increase in IAA secretion by NKZ-259 cells. The results clearly demonstrate that S. fradiae NKZ-259 holds great potential for plant growth promotion and IAA production. Furthermore, kaolin-based powder is an effective carrier for NKZ-259 cells and may be useful for commercial applications.

One-Step Process for Environment-Friendly Preparation of Agar Oligosaccharides From Gracilaria lemaneiformis by the Action of Flammeovirga sp. OC4

Oligosaccharides extracted from agar Gracilaria lemaneiformis (G. lemaneiformis) have stronger physiological activities and a higher value than agar itself, but the pollution caused by the extraction process greatly restricts the sustainable use of agar. In this study, four bacterial strains with a high ability to degrade G. lemaneiformis were isolated from seawater by in situ enrichment in the deep sea. Among them, Flammeovirga sp. OC4, identified by morphological observation and its 16S rRNA sequencing (98.07% similarity to type strain JL-4 of Flammeovirga aprica), was selected. The optimum temperature and pH of crude enzyme produced by Flammeovirga sp. OC4 were 50°C and 8, respectively. More than 60% of the maximum enzyme activity remained after storage at pH 5.0-10.0 for 60 min. Both Mn²⁺ and Ba²⁺ could enhance the enzyme activity. A "one-step process" for preparation of oligosaccharides from G. lemaneiformis was established using Flammeovirga sp. OC4. After optimization of the Plackett-Burman (PB) design and response surface methodology (RSM), the yield of oligosaccharides was increased by 36.1% from 2.71 to 3.09 g L^-1 in a 250-mL fermenter with optimized parameters: 30 g L^-1 G. lemaneiformis powder, 4.84 g L^-1 (NH4)₂SO₄, 44.8-mL working medium volume at 36.7°C, and a shaking speed of 200 × g for 42 h. The extracted oligosaccharides were identified by thin layer chromatography (TLC) and ion chromatography, which consisted of neoagarobiose, agarotriose, neoagarotetraose, agaropentaose, and neoagarohexaose. These results provided an alternative approach for environment-friendly and sustainable utilization of algae.

Modeling and Statistical Optimization of Culture Conditions for Improvement of Antifungal Compounds Production by Streptomyces albidoflavus S19 Strain of Wastewater Origin

BACKGROUND

The actinomycetes strains isolated from unexplored ecosystems are a promising alternative for the biosynthesis of novel antimicrobial compounds. Depending on the interesting antifungal activity of the studied strain S19, the statistical method seems to be an effective tool for optimizing the production of anticandidal molecules.

INTRODUCTION

This study was conducted in order to optimize the culture parameters (medium nutrients concentrations and initial pH value) affecting the production of antifungal metabolites from S. albidoflavus strain S19 (obtained from wastewater collected in Bejaia region, Algeria) using Response Surface Metho-dology (RSM). The best conditions for anti-Candida albicans compounds biosynthesis were determined.

METHODS AND RESULTS

The antimicrobial producer strain S. albidoflavus S19 was identified on the basis of morphological, chemicals characters and physiological characteristics along with 16S rRNA gene se-quencing analysis.Response Surface Methodology by Central Composite Design (CCD) was employed to improve the anti-C. albicans agents production through the optimization of medium parameters. The highest antifungal ac-tivity was obtained by using a mixture of 2g l-1 starch, 4g l-1 yeast extract, 2g l-1 peptone at pH 11.

CONCLUSION

The strain S19 isolated from wastewater showed a significant anti-C. albicans activity and this study revealed the effectiveness of RSM and CCD for increasing bioactive compounds production, rising the diameter of inhibition zones from 13 to 34 mm.

Optimizing Culture Conditions by Statistical Approach to Enhance Production of Pectinase from Bacillus sp. Y1

It was found that Bacillus sp. Y1 could secrete alkaline pectinase with suitable enzyme system for powerful and fast degumming of ramie fiber. In this study, the medium components and fermentation conditions were optimized by some statistical methods including mixture design, fractional factorial design, central composite design and response surface methodology, and single factor method for enhancing the alkaline pectinase production. The optimized conditions for pectinase production were that the culture was shaken at 34°C for 60 h in 50 mL of medium containing 10.5% (w/v) carbon source (consisting of 3.8% starch, 4.2% wheat bran, and 2.5% sucrose), 0.37% (NH₄)₂SO₄, 0.3% MgSO₄, and 0.1% Tween-80, with initial pH 8.2 and inoculation amount of 1.3 mL (with the OD600 of the seed medium about 5.77). Using the optimizing conditions, the activities of polygalacturonate lyase (PGL) and polygalacturonase (PG) in fermentation liquor were increased to 2.00-fold and 3.44-fold, respectively, and the fermentation time shortened 12 hours (from 72 h to 60 h), which showed good application potential in degumming of ramie.

Optimization of Oligosaccharide Production from Leuconostoc lactis Using a Response Surface Methodology and the Immunostimulating Effects of These Oligosaccharides on Macrophage Cells

Production of oligosaccharides from Leuconostoc lactis CCK940 was optimized using a response surface methodology with a central composite design. Culture temperature and the concentrations of sucrose and maltose were used as the main factors. The predicted optimum conditions for the production of oligosaccharides were a culture temperature of 30 °C, a sucrose concentration of 9.6% (w/v), and a maltose concentration of 7.4% (w/v). Using these optimal conditions, Leuconostoc lactis CCK940 was cultured using a fermenter to produce oligosaccharides, and the resulting oligosaccharides with a degree of polymerization greater than 4 were purified by Bio-gel P2 gel permeation column chromatography and then lyophilized. When macrophages were treated with the purified oligosaccharides at concentrations of 0.1⁻10 mg/mL, no cytotoxicity towards the macrophages was observed. However, nitric oxide production levels were similar to those following treatment with 1 μg/mL lipopolysaccharide. The mRNA expression levels of tumor necrosis factor-α, interleukin-1β, interleukin-6, and inducible nitric oxide synthase were all also increased in a dose-dependent manner following treatment with the oligosaccharides. These data suggest that oligosaccharides produced by Leuconostoc lactis CCK940 could be used as an immune enhancer of macrophages.

Enhanced biosynthesis of dextransucrase: A multivariate approach to produce a glucosyltransferase for biocatalysis of sucrose into dextran

The current study reported the statistically designed experimental method to enhance the biocatalytic efficacy of dextransucrase from Weissella confusa. Various environmental and nutritional parameters were optimized using multiple responses under submerged fermentation environment. Statistical models were constructed to screen the influence of nine factors on the biocatalysis of dextransucrase. Among them, fermentation time, pH, sucrose and peptone exhibited significant probability (P < 0.05) and are considered as substantial constituents in accordance with Plackett-Burman design. Central composite design was further implemented to optimize the levels of selected variables for maximum enzyme yield. The predicted optimum conditions were pH of 7.5 under fermentation time of 8 h with 30.0 g l^-1 sucrose and 1.0 g l^-1 peptone. The overall enzyme yield increased from 11.4 DSU ml^-1 to 52.75 DSU ml^-1 with 4.62-fold upsurge after the implementation of the statistical models. Furthermore, SEM analysis showed the biocatalytic conversion of sucrose into highly porous dextran when utilizing dextransucrase. The biopolymer produced under the current optimized model could be utilized as an emulsifying, gelling, stabilizing and thickening agent in food industry.

Application of response surface methodology for optimization of medium components for the production of secondary metabolites by Streptomyces diastatochromogenes KX852460

A bioactive strain Streptomyces diastatochromogenes KX852460 was selected for the production of secondary metabolites to control the target spot disease on tobacco leaves, caused by the Rhizoctonia solani AG-3. Peanut meal, soluble starch, NaCl, yeast extract, and ammonium sulphate were identified the best ingredient for high antifungal activity of S. diastatochromogenes KX852460 against the R. solani AG-3. For the improved production of secondary metabolites, central composite design of response surface methodology was applied in submerged fermentation. The best concentrations of ingredients were peanut meal 4.88%, soluble starch 4.40%, NaCl 0.52%, yeast extract 0.47%, and ammonium sulphate 0.0360%. Study of metabolism changes in the submerged fermentation process was analyzed. Level of the reducing sugar increased, as the total sugar consumed. Amino nitrogen and total sugar decrease tendency, which indicated the growth of bacteria in submerged fermentation batch. Production of secondary and other metabolites influenced the pH of the fermentation batch.

Sugar Beet Pulp as Leuconostoc mesenteroides T3 Support for Enhanced Dextransucrase Production on Molasses

Sugar beet pulp (SBP) and molasses, as an agro industrial waste material, are produced in large amounts annually. Thus, a major challenge nowadays is to develop procedures that could increase the value of the generated waste. In this study, SBP as a support for cell immobilization and molasses as a source of nutrients were used for a dextransucrase (DS) production by Leuconostoc mesenteroides T3. The influence of SBP in native form (SBP-N) and after treatment with NaOH (SBP-NaOH) on DS production was investigated. The optimal medium composition for the maximum DS production was determined by varying the concentration of molasses, SBP, and sucrose. The maximum DS yield of 2.02 U/ml was obtained in the medium with 2.5 % of molasses, 2.5 % SBP-NaOH, and 4 % of sucrose concentration. Scanning electron microscopy (SEM) showed immobilization of Lc. mesenteroides T3 cells onto SBP-NaOH. According to the obtained results, the production of DS on molasses could be improved by using NaOH-treated SBP as a carrier for whole-cell immobilization. Our study reveals the basis for the development of process for DS production with additional reduction of expenses by using waste materials for obtaining the valuable biotechnological product.

Simultaneous efficient removal of high-strength ammonia nitrogen and chemical oxygen demand from landfill leachate by using an extremely high ammonia nitrogen-resistant strain

Bioaugmentation is a promising technology for pollutant elimination from stressed environments, and it would provide an efficient way to solve challenges in traditional biotreatment of wastewater with high strength of ammonia nitrogen (NH4(+)-N). A high NH4(+)-N-resistant bacteria strain, identified as Bacillus cereus (Jlu BC), was domesticated and isolated from the bacteria consortium in landfill leachate. Jlu BC could survive in 100 g/L NH4(+)-N environment, which indicated its extremely high NH4(+)-N tolerance than the stains found before. Jlu BC was employed in the bioaugmented system to remove high strength of NH4(+)-N from landfill leachate, and to increase the removal efficiency, response surface methodology (RSM) was used for optimizing bioaugmentation degradation conditions. At the optimum condition (initial pH 7.33, 4.14 days, initial chemical oxygen demand [COD] concentration [18,000 mg/L], 3.5 mL inoculated domesticated bacteria strain, 0.3 mg/mL phosphorus supplement, 30 °C, and 170 rpm), 94.74 ± 3.8% removal rate of NH4(+)-N was obtained, and the experiment data corresponded well with the predicted removal rate of the RSM models (95.50%). Furthermore, COD removal rate of 81.94 ± 1.4% was obtained simultaneously. The results presented are promising, and the screened strain would be of great practical importance in mature landfill leachate and other NH4(+)-N enrichment wastewater pollution control.

Medium optimization for the production of anti-cyanobacterial substances by Streptomyces sp. HJC-D1 using response surface methodology

Bioremediation using isolated anti-cyanobacterial microorganism has been widely applied in harmful algal blooms (HABs) control. In order to improve the secretion of activated anti-cyanobacterial substances, and lower the cost, a sequential optimization of the culture medium based on statistical design was employed for enhancing the anti-cyanobacterial substances production and chlorophyll a (Chl a) removal by Streptomyces sp. HJC-D1 in the paper. Sucrose and KNO3 were selected as the most suitable carbon and nitrogen sources based on the one-at-a-time strategy method, and sucrose, KNO3 and initial pH were found as major factors that affected the anti-cyanobacterial ability of the isolated stain via the Plackett-Burman design. Based on the response surface and canonical analysis, the optimum condition of culture medium was obtained at 22.73 g l(-1) of sucrose, 0.96 g l(-1) of KNO3, and initial pH 8.82, and the Chl a removal efficiency by strain HJC-D1 increased from 63 ± 2 % to 78 ± 2 % on the optimum conditions.

Properties of Geobacillus stearothermophilus levansucrase as potential biocatalyst for the synthesis of levan and fructooligosaccharides

The production of levansucrase (LS) by thermophilic Geobacillus stearothermophilus was investigated. LS production was more effective in the presence of sucrose (1%, w/v) than fructose, glucose, glycerol or raffinose. The results (Top 57°C; stable for 6 h at 47°C) indicate the high stability of the transfructosylation activity of G. stearothermophilus LS as compared with LSs from other microbial sources. Contrary to temperature, the pH had a significant effect on the selectivity of G. stearothermophilus LS-catalyzed reaction, favoring the transfructosylation reaction in the pH range of 6.0-6.5. The kinetic parameter study revealed that the catalytic efficiency of transfructosylation activity was higher as compared with the hydrolytic one. In addition to levan, G. stearothermophilus LS synthesized fructooligosaccharides in the presence of sucrose as the sole substrate. The results also demonstrated the wide acceptor specificity of G. stearothermophilus LS with maltose being the best fructosyl acceptor. This study is the first on the catalytic properties and the acceptor specificity of LS from G. stearothermophilus.

Molecular cloning and characterization of active truncated dextransucrase from Leuconostoc mesenteroides B-1299CB4

The open reading frame of dsrE563, a dextransucrase gene obtained from a constitutive mutant (CB4-BF563) of Leuconostoc mesenteroides B-1299, consists of 8,511 bp encoding 2,836 amino acid residues. DsrE563 contains two catalytic domains (CD1 and CD2). Two truncated derivative mutants DsrE563ΔCD2ΔGBD (DsrE563-1) and DsrE563ΔCD2ΔVR (DsrE563-2) of DsrE563 were constructed and expressed using the pRSETC vector in Escherichia coli. The derivatives DsrE563-1 (deletion of 1,620 amino acids from the C-terminus) and DsrE563-2 (deletion of 1,258 amino acids from the C-terminus and 349 amino acids from the N-terminus) were expressed as active enzymes. Both enzymes synthesized less-soluble dextran, mainly containing α-1,6 glucosidic linkage. The synthesized less-soluble dextran also had a branched α-1,3 linkage. DsrE563-2 showed 4.5-fold higher dextransucrase activity than that of DsrE563-1 and showed higher acceptor reaction efficiency than that of dextransucrase from L. mesenteroides 512 FMCM when various mono or disaccharides were used as acceptors. Thus, the glucan-binding domain was important for both enzyme expression and dextransucrase activity.

Enhancement of Cellulase Activity from a New Strain of Bacillus subtilis by Medium Optimization and Analysis with Various Cellulosic Substrates

The cellulase activity of Bacillus subtilis AS3 was enhanced by optimizing the medium composition by statistical methods. The enzyme activity with unoptimised medium with carboxymethylcellulose (CMC) was 0.07 U/mL and that was significantly enhanced by CMC, peptone, and yeast extract using Placket-Burman design. The combined effects of these nutrients on cellulase activity were studied using 2² full factorial central composite design. The optimal levels of medium components determined were CMC (1.8%), peptone (0.8%), and yeast extract (0.479%). The maximum enzyme activity predicted by the model was 0.49 U/mL which was in good agreement with the experimental value 0.43 U/mL showing 6-fold increase as compared to unoptimised medium. The enzyme showed multisubstrate specificity, showing significantly higher activity with lichenan and β-glucan and lower activity with laminarin, hydroxyethylcellulose, and steam exploded bagasse. The optimised medium with lichenan or β-glucan showed 2.5- or 2.8-fold higher activity, respectively, at same concentration as of CMC.

Enhanced decolourization of Direct Red-80 dye by the white rot fungus Phanerochaete chrysosporium employing sequential design of experiments

Decolourization of Direct Red 80 (DR-80) by the white rot fungus Phanerochaete chrysosporium MTCC 787 was investigated employing sequential design of experiments. Media components for growing the white rot fungus were first screened using Plackett-Burman design and then optimized using response surface methodology (RSM), which resulted in enhancement in the efficiency of dye removal by the fungus. For determining the effect of media constituents on the dye removal, both percent dye decolourization and specific dye removal due to maximum enzyme activity were chosen as the responses from the experiments, and the media constituents glucose, veratryl alcohol, KH(2)PO(4), CaCl(2) and MgSO(4) were screened to be the most effective with P values less than 0.05. Central composite design (CCD) followed by RSM in the optimization study revealed the following optimum combinations of the screened media constituents: glucose, 11.9 g l(-1); veratryl alcohol, 12.03 mM; KH(2)PO(4), 23.08 g l(-1); CaCl(2), 2.4 g l(-1); MgSO(4), 10.47 g l(-1). At the optimum settings of the media constituents, complete dye decolourization (100% removal efficiency) and a maximum specific dye removal due to lignin peroxidase enzyme of 0.24 mg U(-1) by the white rot fungus were observed.