Enhanced production of exocellular glucansucrase from Leuconostoc dextranicum NRRL B-1146 using response surface method

Cutinase production from Fusarium verticillioides using response surface methodology and its application as potential insecticide degrader

Cutinase, a multifunctional enzyme, has shown great potential in environmental applications such as degradation of plastics and some commonly used insecticides. To overcome these environmental threatening problems, attempts should be made to enhance enzyme production. In the present study, a cutinolytic fungus was isolated from the soil. Based on 18 s rDNA sequencing, it was found that isolate AR08 belongs to the genus Fusarium and clades with Fusarium verticillioides. Optimization of medium composition for enhancement in cutinase production was done using. classical and statistical methods. Firstly, key factors were selected by one variable at a time (OVAT) method, then by Plackett- Burman design. Concentration of these important factors was optimized by Central Composite design. A total of 30 experiments were conducted and the optimized concentration of sodium nitrate, dipotassium hydrogen phosphate, flaxseed oil and zinc sulphate were found to be 0.455%, 0.305%, 2% and 0.0355% respectively. The result of ANOVA (analysis of variance) test revealed that p value was significant for the model. Interaction between flaxseed oil and sodium nitrate was found to have a positive effect on cutinase production. A 14.57 fold increase in enzyme activity was found under optimized conditions with the maximum cutinase activity of 626.6 IUml-1.

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.

Bioprospecting of indigenous resources for the exploration of exopolysaccharide producing lactic acid bacteria

Exploration of biodiversity lead towards the discovery of novel exopolysaccharide (EPS) producing microbes that have multiple applications. The safety compatibility status of lactic acid bacteria (LAB) makes it an attractive candidate for the production of EPS in industries. Therefore, new bacterial isolates are continuously being identified from different habitats. Current research was conducted to explore indigenous biodiversity for the production of dextransucrase, which is involved in the synthesis of dextran. Dextran is an EPS which is used in different industries. In this study, thirty-nine LAB were isolated from different food samples. The isolates were identified as genus Leuconostoc, Weissella and Streptococcus based on genotypic and phenotypic characteristics. Screening revealed that only eight isolates can produce dextransucrase in high titres. Fermentation conditions of dextran producing LAB was optimized. The results indicated that Weissella confusa exhibited maximum specific activity (1.50 DSU mg-1) in 8 h at 25 °C with pH 7.5. Dextran produced from Weissella proved to be a useful alternative to commercially used dextran produced by Leuconostoc mesenteroides in industries for various applications.

Influence of Tween-80 on the production and structure of water-insoluble curdlan from Agrobacterium sp

In order to explore the mechanism by which Tween-80 enhances the production of curdlan produced by Agrobacterium sp., the effects of Tween-80 on the production and structure of curdlan and Agrobacterium sp. were evaluated. Maximum curdlan production (51.94g/L) was achieved when 16g/L Tween-80 was added at the beginning of the cell growth stage. The addition of Tween-80 at higher concentration inhibited cell growth. However, the addition of 16g/L Tween-80 enhanced the production of curdlan with a looser ultrastructure, significantly weakened the envelopment of curdlan on Agrobacterium sp., altered the fine structure of cell membrane, and increased the cell membrane permeability. Moreover, the efficiency of oxygen and mass transport, respiration intensity, UTP regeneration, ATP regeneration, activity of curdlan synthetase, capacity of stress response and energy supply of Agrobacterium sp. were all greatly improved by the addition of Tween-80. These findings demonstrate the mechanisms by which Tween-80 enhances curdlan production and provide a cheap and feasible approach to weaken the envelopment of water-insoluble polysaccharides on bacteria.

Hybrid Cross-Linked Lipase Aggregates with Magnetic Nanoparticles: A Robust and Recyclable Biocatalysis for the Epoxidation of Oleic Acid

Highly stable and easily recyclable hybrid magnetic cross-linked lipase aggregates (HM-CSL-CLEAs) were prepared by coaggregation of lipase aggregates with nonfunctionalized magnetic nanoparticles and subsequent chemical cross-linking with glutaraldehyde. Analysis by SEM and CLSM indicated that the CLEAs were embedded in nanoparticle aggregates instead of covalently immobilized. The resulting HM-CSL-CLEAs exhibited higher thermostability, storage stability, and reusability than standard CLEAs. For example, HM-CSL-CLEAs maintained >60% of their initial activity after 40 min of incubation at 60 °C, whereas standard CLEAs lost most of their activities. The HM-CSL-CLEAs can be easily recovered from the reaction mixture by an external magnetic field. Moreover, the H2O2 tolerance of the lipase in HM-CSL-CLEAs was also enhanced, which could relieve the inhibitory effect on lipase activity. A high conversion yield (55%) for the epoxidation of oleic acid using H2O2 as oxidizing agent was achieved by HM-CSL-CLEAs.

Functionalized silica nanoparticles as a carrier for Betamethasone Sodium Phosphate: Drug release study and statistical optimization of drug loading by response surface method

Mesoporous silica nanoparticles with a hexagonal structure (SBA-15) were synthesized and modified with (3-aminopropyl) triethoxysilane (APTES), and their performance as a carrier for drug delivery system was studied. Chemical structure and morphology of the synthesized and modified SBA-15 were characterized by SEM, BET, TEM, FT-IR and CHN technique. Betamethasone Sodium Phosphate (BSP) as a water soluble drug was loaded on the mesoporous silica particle for the first time. The response surface method was employed to obtain the optimum conditions for the drug/silica nanoparticle preparation, by using Design-Expert software. The effect of time, pH of preparative media, and drug/silica ratio on the drug loading efficiency was investigated by the software. The maximum loading (33.69%) was achieved under optimized condition (pH: 1.8, time: 3.54 (h) and drug/silica ratio: 1.7). The in vitro release behavior of drug loaded particles under various pH values was evaluated. Finally, the release kinetic of the drug was investigated using the Higuchi and Korsmeyer-Peppas models. Cell culture and cytotoxicity assays revealed the synthesized product doesn't have any cytotoxicity against human bladder cell line 5637. Accordingly, the produced drug-loaded nanostructures can be applied via different routes, such as implantation and topical or oral administration.

Factors affecting viability of Bifidobacterium bifidum during spray drying

Background

There is substantial clinical data supporting the role of Bifidobacterium bifidum in human health particularly in benefiting the immune system and suppressing intestinal infections. Compared to the traditional lyophilization, spray-drying is an economical process for preparing large quantities of viable microorganisms. The technique offers high production rates and low operating costs but is not usually used for drying of substances prone to high temperature. The aim of this study was to establish the optimized environmental factors in spray drying of cultured bifidobacteria to obtain a viable and stable powder.

Methods

The experiments were designed to test variables such as inlet air temperature, air pressure and also maltodextrin content. The combined effect of these variables on survival rateand moisture content of bacterial powder was studied using a central composite design (CCD). Sub-lethal heat-adaptation of a B. bifidum strain which was previously adapted to acid-bile-NaCl led to much more resistance to high outlet temperature during spray drying. The resistant B. bifidum was supplemented with cost friendly permeate, sucrose, yeast extract and different amount of maltodextrin before it was fed into a Buchi B-191 mini spray-dryer.

Results

Second-order polynomials were established to identify the relationship between the responses andthe three variables. Results of verification experiments and predicted values from fitted correlations were in close agreement at 95% confidence interval. The optimal values of the variables for maximum survival and minimum moisture content of B. bifidum powder were as follows: inlet air temperature of 111.15°C, air pressure of 4.5 bar and maltodextrin concentration of 6%. Under optimum conditions, the maximum survival of 28.38% was achieved while moisture was maintained at 4.05%.

Conclusion

Viable and cost effective spray drying of Bifidobacterium bifidum could be achieved by cultivating heat and acid adapted strain into the culture media containing nutritional protective agents.

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.

Investigation and optimization of the novel UASB-MFC integrated system for sulfate removal and bioelectricity generation using the response surface methodology (RSM)

COD/sulfate ratio and hydraulic residence time (HRT), both of which influence sulfate loadings jointly, are recognized as the most two important affecting factors for sulfate removal and bioelectricity generation in the novel up-flow anaerobic sludge blanket reactor-microbial fuel cell (UASB-MFC) integrated system. The response surface methodology (RSM) was employed for the optimization of this system and the optimum condition with COD/sulfate ratio of 2.3 and HRT of 54.3h was obtained with the target of maximizing the power output. In terms of maximizing the total sulfate removal efficiency, the obtained optimum condition was COD/sulfate ratio of 3.7 and HRT of 55.6h. Experimental results indicated the undistorted simulation and reliable optimized results. These demonstrated that RSM was effective to evaluate and optimize the UASB-MFC system for sulfate removal and energy recovery, providing a promising guide to further improvement of the system for potential applications.

Optimization of parameters for enhanced oil recovery from enzyme treated wild apricot kernels

Present investigation was undertaken with the overall objective of optimizing the enzymatic parameters i.e. moisture content during hydrolysis, enzyme concentration, enzyme ratio and incubation period on wild apricot kernel processing for better oil extractability and increased oil recovery. Response surface methodology was adopted in the experimental design. A central composite rotatable design of four variables at five levels was chosen. The parameters and their range for the experiments were moisture content during hydrolysis (20-32%, w.b.), enzyme concentration (12-16% v/w of sample), combination of pectolytic and cellulolytic enzyme i.e. enzyme ratio (30:70-70:30) and incubation period (12-16 h). Aspergillus foetidus and Trichoderma viride was used for production of crude enzyme i.e. pectolytic and cellulolytic enzyme respectively. A complete second order model for increased oil recovery as the function of enzymatic parameters fitted the data well. The best fit model for oil recovery was also developed. The effect of various parameters on increased oil recovery was determined at linear, quadric and interaction level. The increased oil recovery ranged from 0.14 to 2.53%. The corresponding conditions for maximum oil recovery were 23% (w.b.), 15 v/w of the sample, 60:40 (pectolytic:cellulolytic), 13 h. Results of the study indicated that incubation period during enzymatic hydrolysis is the most important factor affecting oil yield followed by enzyme ratio, moisture content and enzyme concentration in the decreasing order. Enzyme ratio, incubation period and moisture content had insignificant effect on oil recovery. Second order model for increased oil recovery as a function of enzymatic hydrolysis parameters predicted the data adequately.

Dextransucrase from the mutant of Pediococcus pentosaceus (PPm) is more stable than the wild type

A comparative study on both wild type and mutant of Pediococcus pentosaceus for dextransucrase activity, its stability, dextran synthesizing activity, antibiotic sensitivity and carbohydrate utilization was performed. The wild type P. pentosaceus had specific activity of 0.58 U/mg whereas the mutant showed that of 1.0 U/mg with 72% enhancement. The antibiogram of 27 antibiotics tested against mutant showed significant differences with 9 antibiotics when compared to wild type. In carbohydrate fermentation profile, trehalose, galactose, maltose, lactose and fructose are metabolized by both the strains, but weakly in case of mutant. Stabilization of purified dextransucrase from wild type and mutant with various stabilizers was studied at 30 and 4 °C. Both enzymes were more stable at 4 °C. Among various stabilizers such as dextran (100 kDa, 10 μg/ml), glycerol (0.5%, v/v), PEG 8000 (10 μg/ml) and Tween 80 (0.5%, v/v), Tween 80 provided maximum stabilization at 4 and 30 °C. The mutant showed better stabilization than that of the wild type at both 30 and 4 °C. The loss of activity at 30 °C after 24 h in wild type and mutant in the presence of Tween 80 was only 34 and 32%, respectively, whereas the loss of activity in control of wild type and mutant was 76 and 59%, respectively. After 15 days at 4 °C, the loss of activity in control of wild type and mutant in the presence of Tween 80 was only 15 and 8%, respectively, whereas at 30 °C, the loss of activity in control of wild type and mutant was 49 and 42% respectively. Half-life of the enzyme with Tween 80 was 28.5 and 33.5 h for wild type and mutant, respectively, at 30 °C and 52.1 and 106.6 days for wild type and mutant respectively, at 4 °C.

Comparison of culture methods on exopolysaccharide production in the submerged culture of Cordyceps militaris and process optimization

AIMS

To improve exopolysaccharides (EPS) production of Cordyceps militaris (C. militaris), effects of different culture method on mycelial biomass and EPS production in the submerged culture of C. militaris were investigated.

METHODS AND RESULTS

 A new two-stage fermentation process for EPS production of C. militaris was designed in this work. Central composite design (CCD) was utilized to optimize the two-stage fermentation process. The results showed that the two-stage fermentation process for EPS production was superior to other culture method (conventional static culture and shake culture). CCD revealed that the optimum values of the test variables for EPS production were shaken for 140 h followed by 130-h static culture. The maximum EPS production reached 3·2 g l(-1) under optimized two-stage culture and was about 2·3-fold and 1·6-fold in comparison with those of original static culture and shake culture.

CONCLUSIONS

It was indicated that a new two-stage culture method obtained in this work possessed a high potential for the industrial production for EPS of C. militaris.

SIGNIFICANCE AND IMPACT OF THE STUDY

The fundamental information obtained in this work is complementary to those of previous investigations on the submerged culture of C. militaris for the production of bioactive metabolites.

Modeling and optimization of phenylalanine ammonia lyase stabilization in recombinant Escherichia coli for the continuous synthesis of l-phenylalanine on the statistical-based experimental designs

Some approaches for improving recombinant phenylalanine ammonia lyase (PAL) stability in Escherichia coli during the enzymatic methods of l-phenylalanine (l-Phe) production were developed following preliminary studies by means of statistical-based experiment designs (response surface method). The traditional non-statistical technology was used to screen four critical factors for PAL stability during the bioconversion process, viz., glycerin, sucrose, 1,4-dithiothreitol (DTT), and MgSO(4). The central composite design (CCD) was applied to optimize the combined effect of critical factors for recombinant PAL stability and understand the relationship between the factors and PAL stability. The optimum values for testing variables were 13.04 mM glycerin, 1.87 mM sucrose, 4.09 mM DTT, and 69 mM Mg(2+). A second-order model equation was suggested and then validated experimentally. The model adequacy was very satisfactory because the coefficient of determination was 0.88. The maximum PAL activity was retained as 67.73 units/g after three successive cycles of bioconversion. In comparison to initial PAL activity, the loss of PAL activity was only 22%. PAL activity was enhanced about 23% in comparison to the control (without any stabilizer additives). PAL stability was significantly improved during successive bioconversion. The results obtained here verified the effectiveness of the applied methodology and may be helpful for l-Phe production on an industrial scale.

Process optimization for the production of diosgenin with Trichoderma reesei

Based on the response surface methodology, an effective microbial system for diosgenin production from enzymatic pretreated Dioscorea zingiberensis tubers with Trichoderma reesei was studied. The fermentation medium was optimized with central composite design (3(5)) depended on Plackett-Burmann design which identified significant impacts of peptone, K(2)HPO(4) and Tween 80 on diosgenin yield. The effects of different fermentation conditions on diosgenin production were also studied. Four parameters, i.e. incubation period, temperature, initial pH and substrate concentration were optimized using 4(5) central composite design. The highest diosgenin yield of 90.57% was achieved with 2.67% (w/v) of peptone, 0.29% (w/v) of K(2)HPO(4), 0.73% (w/v) of Tween 80 and 9.77% (w/v) of substrate, under the condition of pH 5.8, temperature 30 degrees C. The idealized incubation time was 6.5 days. After optimization, the product yield increased by 33.70% as compared to 67.74 +/- 1.54% of diosgenin yield in not optimized condition. Scale-up fermentation was carried out in a 5.0 l bioreactor, maximum diosgenin yield of 90.17 +/- 3.12% was obtained at an aeration of 0.80 vvm and an agitation rate of 300 rpm. The proposed microbial system is clean and effective for diosgenin production and thus more environmentally acceptable than the traditional acid hydrolysis.

Artificial intelligence based optimization of exocellular glucansucrase production from Leuconostoc dextranicum NRRL B-1146

Two different artificial intelligence techniques namely artificial neural network (ANN) and genetic algorithm (GA) were integrated for optimizing fermentation medium for the production of glucansucrase. The experimental data reported in a previous study were used to build the neural network. The ANN was trained using the back propagation algorithm. The ANN predicted values showed good agreement with the experimentally reported ones from a response surface based experiment. The concentrations of three medium components: viz Tween 80, sucrose and K2HPO4 served as inputs to the neural network model and the enzyme activity as the output of the model. A model was generated with a coefficient of correlation (R2) of 1.0 for the training set and 0.90 for the test data. A genetic algorithm was used to optimize the input space of the neural network model to find the optimum settings for maximum enzyme activity. This artificial neural network supported genetic algorithm predicted a maximum glucansucrase activity of 6.92U/ml at medium composition of 0.54% (v/v) Tween 80, 5.98% (w/v) sucrose and 1.01% (w/v) K2HPO4. ANN-GA predicted model gave a 6.0% increase of enzyme activity over the regression based prediction for optimized enzyme activity. The maximum enzyme activity experimentally obtained using the ANN-GA designed medium was 6.75+/-0.09U/ml which was in good agreement with the predicted value.

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

To improve dextransucrase production from Leuconostocmesenteroides NRRL B-640 culture medium was screened and optimized using the statistical design techniques of Plackett-Burman and response surface methodology (RSM). Plackett-Burman design with six variables viz. sucrose, yeast extract, K2HPO4, peptone, beef extract and Tween 80 was performed to screen the nutrients that were significantly affecting dextransucrase production. The variables sucrose, K2HPO4, yeast extract and beef extract showed above 90% confidence levels for dextransucrase production and were considered as significant factors for optimization using response surface methodology. 2(4)-central composite design was used for RSM optimization. The experimental results were fitted to a second-order polynomial model which gave a coefficient of determination R2=0.95. The optimized composition of 30g/l sucrose, 18.9g/l yeast extract, 19.4g/l K2HPO4 and 15g/l beef extract gave an experimental value of dextransucrase activity of 10.7U/ml which corresponded well with the predicted value of 10.9U/ml by the model.

Application of response surface methodology for maximizing dextransucrase production from Leuconostoc mesenteroides NRRL B-640 in a bioreactor

The production of dextransucrase from Leuconostoc mesenteroides NRRL B-640 was investigated using statistical approaches. Plackett-Burman design with six variables, viz. sucrose, yeast extract, K(2)HPO(4), peptone, beef extract, and Tween 80, was used to screen the nutrients that significantly affected the dextransucrase production. 2(4)-Central composite design with four selected variables (sucrose, K(2)HPO(4), yeast extract, and beef extract) was used for response surface methodology (RSM) for optimizing the enzyme production. The culture was grown under flask culture with 100 ml optimized medium containing 30 g/l sucrose, 18.5 g/l yeast extract, 15.3 g/l K(2)HPO(4), and 5 g/l beef extract at 25 degrees C and shaking at 200 rpm gave dextransucrase with specific activity of 0.68 U/mg. Whereas the same optimized medium in a 3.0-l bioreactor (1.4 l working volume) gave an experimentally determined value of specific activity of 0.70 U/mg, which was in perfect agreement with the predicted value of 0.65 U/mg by the statistical model.

An overview of purification methods of glycoside hydrolase family 70 dextransucrase

The enzyme dextransucrase (sucrose:1, 6-α-D-glucan 6-α-glucosyltransferase, EC 2.4.1.5) catalyses the synthesis of exopolysaccharide, dextran from sucrose. This class of polysaccharide has been extensively exploited in pharmaceutical industry as blood volume expander, as stabiliser in food industry and as a chromatographic medium in fine chemical industry because of their nonionic nature and stability. Majority of the dextrans are synthesized from sucrose by dextransucrase secreted mainly by bacteria belonging to genera Leuconostoc, Streptococcus and Lactobacillus. Bulk of the information on purification of extracellular dextransucrase has been generated from Leuconostoc species. Various methods such as precipitation by ammonium sulphate, ethanol or polyethylene glycol, phase partitioning, ultrafiltration and chromatography have been used to purify the enzyme. Purification of dextransucrase is rendered difficult by the presence of viscous dextran in the medium. However, processes like ultra-filtration, salt and PEG precipitation, chromatography and phase partitioning have been standardized and successfully used for higher scale purification of the enzyme. A recombinant dextransucrase from Leuconostoc mesenteroides B-512F with a histidine tag has been expressed in E. coli cells and purifi ed by immobilized metal ion chromatography. This review reports the available information on purifi cation methods of dextransucrase from Leuconostoc mesenteroides strains.