Optimization of culture variables for improving glucoamylase production by alginate-entrapped Thermomucor indicae-seudaticae using statistical methods

Production, Characterization, Kinetics, and Thermodynamics Analysis of Amyloglucosidase from Fungal Consortium

The current study aimed to produce an amyloglucosidase enzyme from the fungal consortium. The best amylolytic fungal consortia were identified as Alternaria alternata and Aspergillus niger through the 18S rDNA technique. Fermentation kinetics and various nutritional and cultural parameters were analyzed. Maximum production was obtained in M4 media, pH 5.5, 30 °C, and 4 mL inoculum at 150 rpm after 72 h of incubation. Along with that, sodium nitrate at 2.5%, maltose, beef extract 1%, zinc sulfate (0.1%), and Tween 80 (0.1%) supported the maximum amyloglucosidase production. Amyloglucosidase was partially purified up to 1.6 purification fold with a specific activity of 1.84 Umg-1 in a stepwise manner by ammonium sulfate purification, dialysis, and ion exchange chromatography. The AMG enzyme also revealed maximum activity at 50 °C with 5.0 pH. Upon the kinetic analysis, the specific yield coefficient Yp/x and volumetric rates Qp and Qx were also found to be significant in the above optimized conditions. The Km value 0.33 mg mL-1 and Vmax 26.31 U mL-1 were obtained at 1% soluble starch substrate. Thermodynamic parameters for soluble starch hydrolysis were as follows: ΔH = 48.78 kJ mol-1, (Ea) =  - 46.0 kJ mol-1, and ΔS =  - 43.10 J mol-1 K-1. This finding indicates the indigenously isolated fungal consortium can be the best candidate for industrial applications.

Microbial glucoamylases: structural and functional properties and biotechnological uses

Glucoamylases (GAs) are one of the principal groups of enzymes involved in starch hydrolysis and belong to the glycosylhydrolase family. They are classified as exo-amylases due to their ability to hydrolyze α-1,4 glycosidic bonds from the non-reducing end of starch, maltooligosaccharides, and related substrates, releasing β-D-glucose. Structurally, GAs possess a characteristic catalytic domain (CD) with an (α/α)6 fold and exhibit five conserved regions within this domain. The CD may or may not be linked to a non-catalytic domain with variable functions depending on its origin. GAs are versatile enzymes with diverse applications in food, biofuel, bioplastic and other chemical industries. Although fungal GAs are commonly employed for these purposes, they have limitations such as their low thermostability and an acidic pH requirement. Alternatively, GAs derived from prokaryotic organisms are a good option to save costs as they exhibit greater thermostability compared to fungal GAs. Moreover, a group of cold-adapted GAs from psychrophilic organisms demonstrates intriguing properties that make them suitable for application in various industries. This review provides a comprehensive overview of the structural and sequential properties as well as biotechnological applications of GAs in different industrial processes.

Roles of Fe-C amendment on sulfate-containing pharmaceutical wastewater anaerobic treatment: Microbial community and sulfur metabolism

The effects of multiple two-phase anaerobic treatment involving acidification coupling Fe-C on sulfate-containing chemical synthesis-based pharmaceutical wastewater treatment were investigated. Fe-C was added as a filler with 25% vol. to acidogenic reactors for semi-continuous operation. The results suggested that Fe-C amendment promoted sulfate removal efficiency by 47.5% and shortened the reaction time by 50% in the acidogenic phase. With mitigation of sulfate inhibition, SCOD removal efficiency and methane production were further increased by 24.6% and 398% compared to direct raw wastewater anaerobic digestion, respectively, in methanogenic phase. The results of sulfate removal kinetics confirmed a 150% increase of removal rate in acidogenic phase. However, the apparent kinetic microbial sulfate removal constant without Fe-C amendment was maintained at approximately 0.06 h^-1. The Fe-C amendment not only increased the relative abundance of Methanothrix and Desulfovibrio for sulfate reduction but also enriched unclassified_p__Chloroflexi and unclassified_c__Deltaproteobacteria for acidification. Metagenomic results indicated that Fe-C enhanced dissimilatory sulfate reduction and PAPS synthesis of assimilatory step. The hydrogen sulfide production through the 3-mercaptopyruvate to pyruvate pathways was also enhanced. Butyrate-oxidizing genes were increased synchronously to convert butyrate to acetate.

Synergistic effects of multiple enzymes from industrial Aspergillus niger strain O1 on starch saccharification

BACKGROUND

Starch is one of the most important renewable polysaccharides in nature for production of bio-ethanol. The starch saccharification step facilitates the depolymerization of starch to yield glucose for biofuels production. The filamentous fungus Aspergillus niger (A. niger) is the most used microbial cell factory for production of the commercial glucoamylase. However, the role of each component in glucoamylases cocktail of A. niger O1 for starch saccharification remains unclear except glucoamylase.

RESULTS

In this study, we identified the key enzymes contributing to the starch saccharification process are glucoamylase, α-amylase and acid α-amylase out of 29 glycoside hydrolases from the 6-day fermentation products of A. niger O1. Through the synergistic study of the multienzymes for the starch saccharification in vitro, we found that increasing the amount of α-amylase by 5-10 times enhanced the efficiency of starch saccharification by 14.2-23.2%. Overexpression of acid α-amylase in strain O1 in vivo increased the total glucoamylase activity of O1 cultures by 15.0%.

CONCLUSIONS

Our study clarifies the synergistic effects among the components of glucoamylases cocktail, and provides an effective approach to optimize the profile of saccharifying enzymes of strain O1 for improving the total glucoamylase activity.

Biodegradation of endocrine disruptor Bisphenol A by Pseudomonas putida strain YC-AE1 isolated from polluted soil, Guangdong, China

Background

Bisphenol A is an important organic chemical as an intermediate, final and inert ingredient in manufacturing of many important products like polycarbonate plastics, epoxy resins, flame retardants, food–drink packaging coating, and other. BPA is an endocrine disruptor compound that mimics the function of estrogen causing damage to reproductive organs. Bacterial degradation has been consider as a cost effective and eco-friendly method for BPA degradation compared with physical and chemical methods. This study aimed to isolate and identify bacterial strain capable to degrade and tolerate high concentrations of this pollutant, studying the factors affecting the degradation process and study the degradation mechanism of this strain.

Results

YC-AE1 is a Gram negative bacterial strain isolated from soil and identified as Pseudomonas putida by 16S rRNA gene sequence and BIOLOG identification system. This strain found to have a high capacity to degrade the endocrine disruptor Bisphenol A (BPA). Response surface methodology using central composite design was used to statistically optimize the environmental factors during BPA degradation and the results obtained by significant model were 7.2, 30 °C and 2.5% for optimum initial pH, temperature and inoculum size, respectively. Prolonged incubation period with low NaCl concentration improve the biodegradation of BPA. Analysis of variance (ANOVA) showed high coefficient of determination, R² and Adj-R² which were 0.9979 and 0.9935, respectively. Substrate analysis found that, strain YC-AE1 could degrade a wide variety of bisphenol A-related pollutants such as bisphenol B, bisphenol F, bisphenol S, Dibutyl phthalate, Diethylhexyl phthalate and Diethyl phthalate in varying proportion. Pseudomonas putida YC-AE1 showed high ability to degrade a wide range of BPA concentrations (0.5–1000 mg l^− 1) with completely degradation for 500 mg l^− 1 within 72 h. Metabolic intermediates detected in this study by HPLC-MS were identified as 4,4-dihydroxy-alpha-methylstilbene, p-hydroxybenzaldeyde, p-hydroxyacetophenone, 4-hydroxyphenylacetate, 4-hydroxyphenacyl alcohol, 2,2-bis(4-hydroxyphenyl)-1-propanol, 1,2-bis(4-hydroxyphenyl)-2-propanol and 2,2-bis(4-hydroxyphenyl) propanoate.

Conclusions

This study reports Pseudomonas putida YC-AE1 as BPA biodegrader with high performance in degradation and tolerance to high BPA concentration. It exhibited strong degradation capacity and prominent adaptability towards a wide range of environmental conditions. Moreover, it degrades BPA in a short time via two different degradation pathways.

The Development of a Sorghum Bran-Based Biorefining Process to Convert Sorghum Bran into Value Added Products

Sorghum bran, a starch rich food processing waste, was investigated for the production of glucoamylase in submerged fungal fermentation using Aspergillus awamori. The fermentation parameters, such as cultivation time, substrate concentration, pH, temperature, nitrogen source, mineral source and the medium loading ratio were investigated. The glucoamylase activity was improved from 1.90 U/mL in an initial test, to 19.3 U/mL at 10% (w/v) substrate concentration, pH 6.0, medium loading ratio of 200 mL in 500 mL shaking flask, with the addition of 2.5 g/L yeast extract and essential minerals. Fermentation using 2 L bioreactors under the optimum conditions resulted in a glucoamylase activity of 23.5 U/mL at 72 h, while further increase in sorghum bran concentration to 12.5% (w/v) gave an improved gluco-amylase activity of 37.6 U/mL at 115 h. The crude glucoamylase solution was used for the enzymatic hydrolysis of the sorghum bran. A sorghum bran hydrolysis carried out at 200 rpm, 55 °C for 48 h at a substrate loading ratio of 80 g/L resulted in 11.7 g/L glucose, similar to the results obtained using commercial glucoamylase. Large-scale sorghum bran hydrolysis in 2 L bioreactors using crude glucoamylase solution resulted in a glucose concentration of 38.7 g/L from 200 g/L sorghum bran, corresponding to 94.1% of the theoretical hydrolysis yield.

An Insight Into Ameliorating Production, Catalytic Efficiency, Thermostability and Starch Saccharification of Acid-Stable α-Amylases From Acidophiles

Most of the extracellular enzymes of acidophilic bacteria and archaea are stable at acidic pH with a relatively high thermostability. There is, however, a dearth of information on their acid stability. Although several theories have been postulated, the adaptation of acidophilic proteins to low pH has not been explained convincingly. This review highlights recent developments in understanding the structure and biochemical characteristics, and production of acid-stable and calcium-independent α-amylases by acidophilic bacteria with special reference to that of Bacillus acidicola.

Enhancement of methane production in anaerobic digestion of sewage sludge by thermal hydrolysis pretreatment

This study was performed to optimize thermal hydrolysis pretreatment (THP) of sewage sludge for enhanced anaerobic digestion (AD). Using the response surface methodology (RSM), the optimal conditions were found 180 °C of reaction temperature and 76 min of reaction time. Through THP under optimal conditions, high molecular substances in sewage sludge such as soluble microbial by-products (SMPs) and extracellular polymeric substances (EPSs) were hydrolyzed into low molecular ones without the generation of refractory compounds. The microbial community analysis revealed that relative abundances of Methanomicrobia such as Methanosarcina, Methanosaeta (acetoclastic methanogens), and Methanoculleus (hydrogenotrophic methanogens) in AD with THP were higher than those in conventional AD.

Free and immobilized Aspergillus oryzae SBS50 producing protease-resistant and thermostable phytase

Optimization for enhanced phytase production by Aspergillus oryzae SBS50 in submerged fermentation was investigated using Taguchi design. In first step design, starch, beef extract, magnesium sulphate, ferrous sulphate and Tween 80 were identified as significant factors affecting phytase production. These significant factors were further optimized at four different levels using a second Taguchi design and were observed that 1% starch, 2% beef extact, 3% Tween 80, 0.1% magnesium sulphate and 0.225% ferrous sulphate supported maximum phytase production (47,432 U/L). The use of Taguchi designed experiments resulted in 14.9-fold enhancement in phytase production compared to the medium optimized by 'one variable at a time' approach. Furthermore, 4% agar immobilized conidiospores of A. oryzae supported high phytase production compared with free cells and other matrices. Agar-immobilized conidiospores resulted in sustained phytase production up to eight repeated batch cycles followed by a decrease in enzyme titres.

Bioprocess for the production of recombinant HAP phytase of the thermophilic mold Sporotrichum thermophile and its structural and biochemical characteristics

Thermophilc mold Sporotrichum thermophile secretes an acidstable and thermostable phytase, which finds application as a food and feed additive because of its adequate thermostability, acid stability, protease insensitivity and broad substrate spectrum. Low extracellular phytase production by the mold is a major bottleneck for its application on a commercial scale. We have successfully overcome this problem by constitutive secretary expression of codon optimized rStPhy under glyceraldehyde phosphate dehydrogenase (GAP) promoter in Pichia pastoris. A ∼41-fold improvement in rStPhy production has been achieved. Circular Dichroism (CD) spectra revealed that rStPhy is composed of 26.65% α-helices, 5.26% β-sheets and 68.09% random coils at pH 5.0 and 60°C, the optima for the enzyme activity. The melting temperature (T_m) of the enzyme is ∼73°C. The 3D structure of rStPhy displayed characteristic signature sequences (RHGXRXP and HD) of HAP phytase. The catalytically important amino acids (Arg74, His75, Arg78, His368 and Asp369) were identified by docking and site directed mutagenesis. Fluorescence quenching by N-bromosuccinimide (NBS) and CsCl exposed tryptophan residues surrounded by negative charges, which play a key role in maintaining structural integrity of rStPhy.

Bacterial and Archaeal α-Amylases: Diversity and Amelioration of the Desirable Characteristics for Industrial Applications

Industrial enzyme market has been projected to reach US$ 6.2 billion by 2020. Major reasons for continuous rise in the global sales of microbial enzymes are because of increase in the demand for consumer goods and biofuels. Among major industrial enzymes that find applications in baking, alcohol, detergent, and textile industries are α-amylases. These are produced by a variety of microbes, which randomly cleave α-1,4-glycosidic linkages in starch leading to the formation of limit dextrins. α-Amylases from different microbial sources vary in their properties, thus, suit specific applications. This review focuses on the native and recombinant α-amylases from bacteria and archaea, their production and the advancements in the molecular biology, protein engineering and structural studies, which aid in ameliorating their properties to suit the targeted industrial applications.

Strain selection and medium optimization for glucoamylase production from industrial potato waste by Aspergillus niger

BACKGROUND

Glucoamylase is one of the most common enzymes used in the food industry to break down starch into its monomers. Glucoamylase production and its activity are highly dependent on medium composition. Starch is well known as a glucoamylase inducer, and utilization of industrial starchy potato waste is an inexpensive way of improving glucoamylase production. Since glucoamylase production is highly dependent on medium composition, in this study medium optimization for glucoamylase production was considered to enhance glucoamylase activity.

RESULTS

Among the evaluated microbial species, Aspergillus niger van Tieghem was found to be the best glucoamylase-producing fungus. The Plackett-Burman design was used to screen various medium ingredients, and malt extract, FeSO4 .7H2 O and CaCl2 ·2H2 O were found to have significant effects on glucoamylase production. Finally, malt extract, FeSO4 .7H2 O and CaCl2 .2H2 O were optimized by using a central composite design of response surface methodology. The results showed that the optimal medium composition for A. niger van Tieghem was 50 g L(-1) industrial waste potato mash supplemented with 51.82 g L(-1) malt extract, 9.27 g L(-1) CaCl2 ·2H2 O and 0.50 g L(-1) FeSO4 .7H2 O.

CONCLUSION

At the end of optimization, glucoamylase activity and glucose production were improved 126% and 98% compared to only industrial waste potato mash basal medium; 274.4 U mL(-1) glucoamylase activity and 41.7 g L(-1) glucose levels were achieved, respectively. © 2015 Society of Chemical Industry.

Optimization of factors affecting hexavalent chromium removal from simulated electroplating wastewater by synthesized magnetite nanoparticles

Hexavalent chromium is a mutagen and carcinogen that is of significant concern in water and wastewater. In the present study, magnetite nanoparticles (n-Mag) were investigated as a potential remediation technology for the decontamination of Cr (VI)-contaminated wastewater. Synthesized n-Mag was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET-N2 technology. To screen and optimize the factors affecting Cr (VI) removal efficiency by synthesized nanoparticles, Plackett-Burman (PB) and Taguchi experimental designs were used respectively. The crystalline produced n-Mag was in the size range of 60-70 nm and had a specific surface area (SSA) of 31.55 m(2) g(-1). Results of PB design showed that the most significant factors affecting Cr (VI) removal efficiency were initial Cr (VI) concentration, pH, n-Mag dosage, and temperature. In a pH of 2, 20 mg L(-1) of Cr (VI) concentration, 4 g L(-1)of n-Mag, temperature of 40 °C, 220 rpm of shaking speed, and 60 min of contact time, the complete removal efficiency of Cr (VI) was achieved. Batch experiments revealed that the removal of Cr (VI) by n-Mag was consistent with pseudo-second order reaction kinetics. The competition from common coexisting ions such as NO₃(-), SO₄(2-), and Cl(-) were not considerable, unless in the higher concentration of SO₄(2-). These results indicated that the readily synthesized magnetite nanoparticles have promising applications for the removal of Cr (VI) from aqueous solution.

Sequential Statistical Optimization of Media Components for the Production of Glucoamylase by Thermophilic Fungus Humicola grisea MTCC 352

Glucoamylase is an industrially important enzyme which converts soluble starch into glucose. The media components for the production of glucoamylase from thermophilic fungus Humicola grisea MTCC 352 have been optimized. Eight media components, namely, soluble starch, yeast extract, KH2PO4, K2HPO4, NaCl, CaCl2, MgSO4 ·7H2O, and Vogel's trace elements solution, were first screened for their effect on the production of glucoamylase and only four components (soluble starch, yeast extract, K2HPO4, and MgSO4 ·7H2O) were identified as statistically significant using Plackett-Burman design. It was fitted into a first-order model (R (2) = 0.9859). Steepest ascent method was performed to identify the location of optimum. Central composite design was employed to determine the optimum values (soluble starch: 28.41 g/L, yeast extract: 9.61 g/L, K2HPO4: 2.42 g/L, and MgSO4 ·7H2O: 1.91 g/L). The experimental activity of 12.27 U/mL obtained was close to the predicted activity of 12.15. High R (2) value (0.9397), low PRESS value (9.47), and AARD values (2.07%) indicate the accuracy of the proposed model. The glucoamylase production was found to increase from 4.57 U/mL to 12.27 U/mL, a 2.68-fold enhancement, as compared to the unoptimized medium.

Production of cellulase-free xylanase by the recombinant Bacillus subtilis and its applicability in paper pulp bleaching

A metagenomic xylanase gene (Mxyl) was successfully cloned into shuttle vector pWH1520 and expressed in Bacillus subtilis extracellularly. On induction with xylose, recombinant xylanase secretion commenced after 6 h. Identifying critical variables for recombinant xylanase production by one-variable-at-time approach followed by optimization of the selected variables (xylose, inoculum density, incubation density) by response surface methodology (RSM) led to three-fold enhancement in extracellular xylanase production (119 U mL(-1) ). When the pulp was treated with recombinant xylanase at 80°C and pH 9.0, kappa number of the pulp was reduced with concomitant increase in brightness and 24% reduction in chlorine consumption. This is the first report on the expression of metagenomic xylanase gene in Bacillus subtilis extracellularly and its utility in developing an environment-friendly pulp bleaching process.

Studies on process optimization methods for rapamycin production using Streptomyces hygroscopicus ATCC 29253

Rapamycin is a high-value product finding immense use as a drug, in organ transplantation, and as a potential immunosuppressant. Optimization of fermentation parameters of rapamycin production by Streptomyces hygroscopicus NRRL 5491 has been carried out. The low titer value of rapamycin in the original producer strain limits its applicability at industrial level. This study aims at improving the production of rapamycin by optimizing the nutrient requirements. Addition of L-lysine increased the production of rapamycin up to a significant level which supports the fact that it acts as precursor for rapamycin production, as found in previous studies. Effect of optimized medium on the Streptomyces growth rate as well as rapamycin production has been studied. The optimization study incorporates one at a time parameter optimization studies followed by tool-based hybrid methodology. This methodology includes the Plackett-Burman design (PBD) method, artificial neural networks (ANN), and genetic algorithms (GA). PBD screened mannose, soyabean meal, and L-lysine concentrations as significant factors for rapamycin production. ANN was used to construct rapamycin production model. This strategy has led to a significant increase of rapamycin production up to 320.89 mg/L at GA optimized concentrations of 25.47, 15.39, and 17.48 g/L for mannose, soyabean meal, and L-lysine, respectively. The present study must find its application in scale-up study for industrial level production of rapamycin.

Preservation of Bacillus firmus strain 37 and optimization of cyclodextrin biosynthesis by cells immobilized on loofa sponge

The preservation of Bacillus firmus strain 37 cells by lyophilization was evaluated and response surface methodology (RSM) was used to optimize the β-cyclodextrin (β-CD) production by cells immobilized on loofa sponge. Interactions were studied with the variables temperature, pH and dextrin concentration using a central composite design (CCD). Immobilization time influence on β-CD production was also investigated. B. firmus strain 37 cells remained viable after one year of storage, showing that the lyophilization is a suitable method for preservation of the microorganism. From the three-dimensional diagrams and contour plots, the best conditions for β-CD production were determined: temperature 60 °C, pH 8, and 18% dextrin. Considering that the amount of dextrin was high, a new assay was carried out, in which dextrin concentrations of 10, 15, and 18% were tested and the temperature of 60 °C and pH 8 were maintained. The results achieved showed very small differences and therefore, for economic reasons, the use of 10% dextrin is suggested. Increasing the immobilization time of cells immobilized on synthetic sponge the β-CD production decreased and did not change for cells immobilized on loofa sponge. The results of this research are important for microorganism preservation and essential in the optimization of the biosynthesis of CD.

Optimization of cold-adapted lysozyme production from the psychrophilic yeast Debaryomyces hansenii using statistical experimental methods

Statistical experimental designs were employed to optimize culture conditions for cold-adapted lysozyme production of a psychrophilic yeast Debaryomyces hansenii. In the first step of optimization using Plackett-Burman design (PBD), peptone, glucose, temperature, and NaCl were identified as significant variables that affected lysozyme production, the formula was further optimized using a four factor central composite design (CCD) to understand their interaction and to determine their optimal levels. A quadratic model was developed and validated. Compared to the initial level (18.8 U/mL), the maximum lysozyme production (65.8 U/mL) observed was approximately increased by 3.5-fold under the optimized conditions.

PRACTICAL APPLICATION

Cold-adapted lysozymes production was first optimized using statistical experimental methods. A 3.5-fold enhancement of microbial lysozyme was gained after optimization. Such an improved production will facilitate the application of microbial lysozyme. Thus, D. hansenii lysozyme may be a good and new resource for the industrial production of cold-adapted lysozymes.

Kinetics of improved 1,4-alpha-D-glucan glucohydrolase biosynthesis from a newly isolated Aspergillus oryzae IIB-6 and parameter significance analysis by 2-factorial design

Sixteen different mould cultures viz. Aspergillus, Alternaria, Arthroderma, Trichoderma, Fusarium, Penicillium, Rhizopus and Chochliobolus were isolated from the soil samples of Qatar by serial dilution method. The preliminary screening of isolates was done by selecting initial colonies showing relatively bigger zones of starch hydrolysis on nutrient agar plates. The isolates were then subjected to secondary screening by submerged fermentation (SmF). The 1,4-α-D-glucan glucohydrolase (GGH) activity ranged from 1.906-12.675 U/ml/min. The product yield was analysed in dependence of mycelial morphology, biomass level and protein content. The isolate Aspergillus oryzae llB-6 which gave maximum enzyme production was incubated in M3 medium containing 20 g/l starch, 10 g/l lactose, 8.5 g/l yeast extract, 6 g/l corn steep liquor (CSL), 1.2 g/l MgSO₄.7H₂O, 1.3 g/l NH₄Cl, 0.6 g/l CaCl₂.2H₂O, pH 5 at 30±2°C and 200 rpm. On the basis of kinetic variables, notably Q_p (0.058±0.01^a U/g/h), Y_p/s (0.308±0.03^ab U/g) and q_p (0.210±0.032^abc U/g fungal biomass/h), A. oryzae IIB-6 was found to be a hyper producer of GGH (LSD 0.0345) compared to A. kawachii IIB-2. A noticeable enhancement in enzyme activity of over 30% was observed (13.917±1.01 U/ml/min) when the process parameters viz. cultural conditions (pH 5, incubation period 72 h) and nutritional requirements (6 g/l CSL, 9.5 g/l yeast extract, 10 g/l starch, 20 g/l lactose) were further optimized using a 2-factorial Plackett-Burman design. The model terms were found to be highly significant (HS, p≤0.05), indicating the potential utility of the culture (dof~3).

Optimization of fermentation medium for triterpenoid production from Antrodia camphorata ATCC 200183 using artificial intelligence-based techniques

In this study, alteration in morphology of submergedly cultured Antrodia camphorata ATCC 200183 including arthroconidia, mycelia, external and internal structures of pellets was investigated. Two optimization models namely response surface methodology (RSM) and artificial neural network (ANN) were built to optimize the inoculum size and medium components for intracellular triterpenoid production from A. camphorata. Root mean squares error, R (2), and standard error of prediction given by ANN model were 0.31%, 0.99%, and 0.63%, respectively, while RSM model gave 1.02%, 0.98%, and 2.08%, which indicated that fitness and prediction accuracy of ANN model was higher when compared to RSM model. Furthermore, using genetic algorithm (GA), the input space of ANN model was optimized, and maximum triterpenoid production of 62.84 mg l(-1) was obtained at the GA-optimized concentrations of arthroconidia (1.78 × 10⁵ ml(-1)) and medium components (glucose, 25.25 g l(-1); peptone, 4.48 g l(-1); and soybean flour, 2.74 g l(-1)). The triterpenoid production experimentally obtained using the ANN-GA designed medium was 64.79 ± 2.32 mg l(-1) which was in agreement with the predicted value. The same optimization process may be used to optimize many environmental and genetic factors such as temperature and agitation that can also affect the triterpenoid production from A. camphorata and to improve the production of bioactive metabolites from potent medicinal fungi by changing the fermentation parameters.

Production and characterization of fengycin by indigenous Bacillus subtilis F29-3 originating from a potato farm

Fengycin, a lipopeptide biosurfactant, was produced by indigenous Bacillus subtilis F29-3 isolated from a potato farm. Although inhibiting the growth of filamentous fungi, the fengycin is ineffective against yeast and bacteria. In this study, fengycin was isolated from fermentation broth of B. subtilis F29-3 via acidic precipitation (pH 2.0 with 5 N HCl) followed by purification using ultrafiltration and nanofiltration. The purified fengycin product was characterized qualitatively by using fast atom bombardment-mass spectrometer, Fourier transform infrared spectrometer, ultraviolet-visible spectrophotometer, ¹³C-nuclear magnetic resonance spectrometer and matrix assisted laser desorption ionization-time of flight, followed by quantitative analysis using reversed-phase HPLC system. This study also attempted to increase fengycin production by B. subtilis F29-3 in order to optimize the fermentation medium constituents. The fermentation medium composition was optimized using response surface methodology (RSM) to increase fengycin production from B. subtilis F29-3. According to results of the five-level four-factor central composite design, the composition of soybean meal, NaNO₃, MnSO₄·4H₂O, mannitol-mannitol, soybean meal-mannitol, soybean meal-soybean meal, NaNO₃-NaNO₃ and MnSO₄·4H₂O-MnSO₄·4H₂O significantly affected production. The simulation model produced a coefficient of determination (R²) of 0.9043, capable of accounting for 90.43% variability of the data. Results of the steepest ascent and central composite design indicated that 26.2 g/L of mannitol, 21.9 g/L of soybean meal, 3.1 g/L of NaNO₃ and 0.2 g/L of MnSO₄·4H₂O represented the optimal medium composition, leading to the highest production of fengycin. Furthermore, the optimization strategy increased the fengycin production from 1.2 g/L to 3.5 g/L.

Improvement in cell-bound phytase activity of Pichia anomala by permeabilization and applicability of permeabilized cells in soymilk dephytinization

AIMS

Whole cell permeabilization of Pichia anomala to ameliorate the cell-bound phytase activity and usability of permeabilized cells in dephytinization of soymilk.

METHODS AND RESULTS

The cells of P. anomala were subjected to permeabilization using the surfactant Triton X-100 to overcome the permeability barrier and prepare whole cell biocatalysts with high phytase activity. The statistical approach, response surface methodology (RSM) was used to optimize the operating conditions for permeabilization. The treatment of cells with 5% Triton X-100 for 30 min resulted in c. 15% enhancement in cell-bound phytase activity. The shrinkage of protoplast was observed, although cell viability and phytase stability were not significantly altered. The free as well as immobilized permeabilized cells hydrolysed soymilk phytate, and the latter could be reused over four consecutive cycles.

CONCLUSIONS

Whole cell permeabilization of P. anomala using Triton X-100 led to enhancement in cell-bound phytase activity. The viability and integrity of yeast cells were not significantly affected because of permeabilization. The permeabilized P. anomala cells effectively dephytinized soymilk, and the permeabilized cells immobilized in alginate could be reused because of sustained phytase activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report on the use of permeabilized yeast cells for mitigating phytate content of soymilk. Alginate entrapment of permeabilized P. anomala allows reuse of cells for soymilk dephytinization, thus suggesting a potential application in food industry.

A novel medium for the production of cephamycin C by Nocardia lactamdurans using solid-state fermentation

In this study, Nocardia lactamdurans NRRL 3802 was explored for the first time for production of cephamycin C by using solid-state fermentation. The effects of various substrates, moisture content, inoculum size, initial pH of culture medium, additional nitrogen source and amino acids were investigated for the maximum production of cephamycin C by N. lactamdurans NRRL 3802 in solid-state fermentation. Subsequently, selected fermentation parameters were further optimized by response surface methodology (RSM). The soybean flour as a substrate with moisture content of 65%, initial pH of culture medium of 6.5 and inoculum size of 10(9)CFU/ml (2 x 10(8)CFU/gds) at 28+/-2 degrees C after 4 days gave maximum production of 15.75+/-0.27 mg/gds of cephamycin C as compared to 8.37+/-0.23 mg/gds before optimization. Effect of 1,3-diaminopropane on cephamycin C production was further studied, which further increased the yield to 27.64+/-0.33 mg/gds.

Kinetic adsorption of application of carbon nanotubes for Pb(II) removal from aqueous solution

The capability of carbon nanotubes (CNTs) to adsorb lead (Pb) in aqueous solution was investigated. Batch mode adsorption experiment was conducted to determine the effects of pH, agitation speed, CNTs dosage and contact time. The removal of Pb(II) reached maximum value 85% or 83% at pH 5 or 40 mg/L of CNTs, respectively. Higher correlation coefficients from Langmuir isotherm model indicates the strong adsorptions of Pb(II) on the surface of CNTs (adsorption capacity Xm = 102.04 mg/g). The results indicates that the highest percentage removal of Pb (96.03%) can be achieved at pH 5, 40 mg/L of CNTs, contact time 80 min, and agitation speed 50 r/min.

Optimization of culture conditions for production of cis-epoxysuccinic acid hydrolase using response surface methodology

Response surface methodology, which allows for rapid identification of important factors and optimization of them to enhance enzyme production, was employed here to optimize culture conditions for the production of cis-epoxysuccinic acid hydrolase from Bordetella sp. strain 1-3. In the first step, a Plackett-Burman design was used to evaluate the effects of nine variables (yeast extract, cis-epoxysuccinic acid, KH(2)PO(4), K(2)HPO(4).3H(2)O, MgSO(4).7H(2)O, trace minerals solution, culture volume, initial pH and incubation time) on the enzyme production. Yeast extract, cis-epoxysuccinic acid and KH(2)PO(4) had significant influences on cis-epoxysuccinic acid hydrolase production and their concentrations were further optimized using central composite design and response surface analysis. A combination of adjusting the concentration of yeast extract to 7.8 g/l, cis-epoxysuccinic acid to 9.8 g/l, and KH(2)PO(4) to 1.12 g/l would favor maximum cis-epoxysuccinic acid hydrolase production. An enhancement of cis-epoxysuccinic acid hydrolase production from 5.6 U/ml to 9.27 U/ml was gained after optimization.

Statistical optimization of process conditions for cellulase production by liquid state bioconversion of domestic wastewater sludge

A two-level fractional factorial design (FFD) was used to determine the effects of six factors, i.e. substrate (domestic wastewater sludge - DWS) and co-substrate concentration (wheat flour - WF), temperature, initial pH, inoculum size and agitation rate on the production of cellulase enzyme by Trichoderma harzianum in liquid state bioconversion. On statistical analysis of the results from the experimental studies, optimum process conditions were found to be temperature 32.5 degrees C, substrate concentration (DWS) 0.75% (w/w), co-substrate (WF) concentration 2% (w/w), initial pH 5, inoculum size 2% (v/w) and agitation 175 rpm. Analysis of variance (ANOVA) showed a high coefficient of determination (R2) of 0.975. Cellulase activity reached 10.2 FPU/ml at day 3 during the fermentation process which indicated about 1.5-fold increase in production compared to the cellulase activity obtained from the results of design of experiment (6.9 FPU/ml). Biodegradation of DWS was also evaluated to verify the efficiency of the bioconversion process as a waste management method.

Optimization of key process variables for enhanced hydrogen production by Enterobacter aerogenes using statistical methods

The individual and mutual effects of glucose concentration, temperature and pH on the hydrogen production by Enterobacter aerogenes were investigated in a batch system. A Box-Behnken design and response surface methodology (RSM) were employed to determine the optimum condition for enhanced hydrogen production. The hydrogen production rate was investigated by simultaneously changing the three independent variables, which all had significant influences on the hydrogen production rate. The maximum hydrogen production rate of 425.8 ml H(2)(g dry cell h)(-1) was obtained under the optimum condition of glucose concentration 118.06 mM, temperature 38 degrees C and pH 6.13. The experimental results showed that the RSM with the Box-Behnken design was a useful tool for achieving high rate of hydrogen production by E. aerogenes.

Medium optimization for enhanced production of cytosine-substituted mildiomycin analogue (MIL-C) by Streptoverticillium rimofaciens ZJU 5119

Cytosine-substituted mildiomycin analogue (MIL-C) was produced effectively by supplementing cytosine into the culture of Streptoverticillium rimofaciens. In order to improve the yield of MIL-C, statistically-based experimental designs were applied to optimize the fermentation medium for S. rimofaciens ZJU 5119. Fifteen culture conditions were examined for their significances on MIL-C production using Plackett-Burman design. The Plackett-Burman design and one-variable-at-a-time design indicated that glucose and rice meal as the complex carbon sources, and peanut cake meal and NH4NO3 as the complex nitrogen sources were beneficial for MIL-C production in S. rimofaciens ZJU 5119. The results of further central composition design (CCD) showed that the optimal concentration of glucose, rice meal and peanut cake meal were 18.7 g/L, 64.8 g/L and 65.1 g/L, respectively. By using this optimal fermentation medium, the MIL-C concentration was increased up to 1336.5 mg/L, an approximate 3.8-fold improvement over the previous concentration (350.0 mg/L) with un-optimized medium. This work will be very helpful to the large-scale production of MIL-C in the future.

Economical glucoamylase production by alginate-immobilized Thermomucor indicae-seudaticae in cane molasses medium

AIMS

The present investigation is aimed at assessing the suitability of cane molasses as a cheaper carbon and energy source for glucoamylase production using alginate-immobilized Thermomucor indicae-seudaticae.

METHODS AND RESULTS

The culture variables for glucoamylase production were optimized by 'one-variable-at-a-time' strategy and response surface methodology (RSM). A high glucoamylase titre was attained when 40 alginate beads (c. 5x10(6) immobilized spores) were used to inoculate 50 ml of cane molasses (8%) medium in 250-ml Erlenmeyer flasks. Response surface optimization of fermentation parameters (cane molasses 7%, inoculum level 44 alginate beads per 50 ml of medium and ammonium nitrate 0.25%) resulted in 1.8-fold higher glucoamylase production (27 U ml(-1)) than that in the unoptimized medium (15 U ml(-1)). Enzyme production was also sustainable in 22 l of laboratory air-lift bioreactor.

CONCLUSIONS

Cane molasses served as an excellent carbon and energy source for the economical production of glucoamylase, which was almost comparable with that in sucrose yeast-extract broth. The statistical model developed using RSM allowed determination of optimum levels of the variables for improving glucoamylase production.

SIGNIFICANCE AND IMPACT OF THE STUDY

The cost of glucoamylase produced in cane molasses supplemented with ammonium nitrate was considerably lower (euro1.43 per million U) than in synthetic medium containing sucrose and yeast-extract (euro35.66 per million U). The reduction in fermentation time in air-lift bioreactor with sustainable glucoamylase titres suggested the feasibility of scale up of the process.