Peptone Concentration Research Articles

Significantly enhancing recombinant alkaline amylase production in Bacillus subtilis by integration of a novel mutagenesis-screening strategy with systems-level fermentation optimization.

BackgroundAlkaline amylase has significant potential for applications in the textile, paper and detergent industries, however, low yield of which cannot meet the requirement of industrial application. In this work, a novel ARTP mutagenesis-screening method and fermentation optimization strategies were used to significantly improve the expression level of recombinant alkaline amylase in B. subtilis 168.ResultsThe activity of alkaline amylase in mutant B. subtilis 168 mut-16# strain was 1.34-fold greater than that in the wild-type, and the highest specific production rate was improved from 1.31 U/(mg·h) in the wild-type strain to 1.57 U/(mg·h) in the mutant strain. Meanwhile, the growth of B. subtilis was significantly enhanced by ARTP mutagenesis. When the agitation speed was 550 rpm, the highest activity of recombinant alkaline amylase was 1.16- and 1.25-fold of the activities at 450 and 650 rpm, respectively. When the concentration of soluble starch and soy peptone in the initial fermentation medium was doubled, alkaline amylase activity was increased 1.29-fold. Feeding hydrolyzed starch and soy peptone mixture or glucose significantly improved cell growth, but inhibited the alkaline amylase production in B. subtilis 168 mut-16#. The highest alkaline amylase activity by feeding hydrolyzed starch reached 591.4 U/mL, which was 1.51-fold the activity by feeding hydrolyzed starch and soy peptone mixture. Single pulse feeding-based batch feeding at 10 h favored the production of alkaline amylase in B. subtilis 168 mut-16#.ConclusionThe results indicated that this novel ARTP mutagenesis-screening method could significantly improve the yield of recombinant proteins in B. subtilis. Meanwhile, fermentation optimization strategies efficiently promoted expression of recombinant alkaline amylase in B. subtilis 168 mut-16#. These findings have great potential for facilitating the industrial-scale production of alkaline amylase and other enzymes, using B. subtilis cultures as microbial cell factories.

Optimization of Levan Production by Cold-Active Bacillus licheniformis ANT 179 and Fructooligosaccharide Synthesis by Its Levansucrase.

Fructooligosaccharides (FOS) and levan attract much attention due to a wide range of applications in food technology and pharmaceutical and cosmetic industry. Bacillus licheniformis ANT 179, isolated from Antarctica soil, produced levansucrase and levan in a medium containing sucrose as carbon substrate. In this study, characterization of levansucrase and production of short-chain FOS and levan were investigated. Temperature and pH optimum of the enzyme were found to be 60°C and pH 6.0, respectively. The optimization of fermentation conditions for levan production using sugarcane juice by response surface methodology (RSM) was carried out. Central composite rotatable design was used to study the main and the interactive effects of medium components: sugarcane juice and casein peptone concentration on levan production by the bacterium. The optimized medium with sugarcane juice at 20% (v/v) and casein peptone at 2% (w/v) was found to be optimal at an initial pH of 7.0 and incubation temperature of 35°C for 48h. Under these conditions, the maximum levan concentration was 50.25g/L on wet weight basis and 16.35g/L on dry weight basis. The produced inulin type FOS (kestose and neokestose) and levan were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) analysis. The study revealed that the levansucrase could form FOS from sucrose. The locally available low-cost substrate such as sugarcane juice in the form of a renewable substrate is proposed to be suitable even for scale-up production of enzyme and FOS for industrial applications. The levan and FOS synthesized by the bacterium are suitable for food applications and biomedical uses as the bacterium has GRAS status and devoid of endotoxin as compared to other Gram-negative bacteria.

Optimization of culture conditions by response surface methodology and unstructured kinetic modeling for bioactive metabolite production by Nocardiopsis litoralis VSM-8.

Response surface methodology-based central composite design on five variables incubation time, pH, temperature, sucrose concentration, and soya peptone concentration was employed for optimization of the production of bioactive compounds by Nocardiopsis litoralis strain VSM 8. The main quadratic effects and interactions of the five variables on the production of bioactive metabolites were investigated. A second-order polynomial model produced a satisfied fit for experimental data with regard to the production of the bioactive metabolites. Regression analysis showed that high R 2 values of all the five responses are significant and adjusted R 2 values showed good agreement with the experimental and predicted values. The present model was used to evaluate the direct interaction and quadratic effects to optimize the physico-chemical parameters for the production of bioactive metabolites that inhibit the pathogenic microorganisms measured in terms of zones of inhibition (responses). Mathematical kinetic model development and estimation of kinetic parameters also showed good approximation in terms of model fitting and regression analysis.

Bioaccumulation of As(III)/As(V) ions by living cells of Corynebacterium glutamicum MTCC 2745

ABSTRACTSignificant factors on simultaneous growth and bioaccumulation of arsenic ions by living cells of bacteria, Corynebacterium glutamicum MTCC 2745, were explored in growth media under experimental conditions like pH and concentrations of arsenic ions. Combined effects of the initial concentrations of peptone and arsenic (either As(III) or As(V)) ions on the specific growth rate and arsenic bioaccumulation competence of the bacteria were studied and optimized using the Response Surface Methodology. Optimum combination predicted via RSM demonstrated that the bacteria were capable of bioaccumulating As(III) and As(V) in the growth medium containing 1000 mg/L arsenic and 9 g/L peptone up to 78.4% and 77.6%, respectively.

Improvement in extracellular protease production by the marine antarctic yeast Rhodotorula mucilaginosa L7

Microorganisms from extreme and restrictive eco systems, such as the Antarctic continent, are of great interest due to their ability to synthesize products of commercial value. Among these, enzymes from psychrotolerant and psychrophilic microorganisms offer potential economical benefits due to their high activity at low and moderate temperatures. The cold adapted yeast Rhodotorula mucilaginosa L7 was selected out of 97 yeasts isolated from Antarctica as having the highest extracellular proteolytic activity in preliminary tests. The present study was aimed at evaluating the effects of nutrient composition (peptone, rice bran extract, ammonium sulfate, sodium chloride) and physicochemical parameters (temperature and pH) on its proteolytic activity. A 26−2 fractional factorial design experiment followed by a central composite design (CCD 23) was performed to optimize the culture conditions and improve the extracellular proteolytic activity. The results indicated that the presence of peptone in the medium was the most influential factor in protease production. Enzymatic activity was enhanced by the interaction between low glucose and peptone concentrations. The optimization of culture conditions with the aid of mathematical modeling enabled a c. 45% increase in proteolytic activity and at the same time reduced the amount of glucose and peptone required for the culture. Thus culture conditions established in this work may be employed in the biotechnological production of this protease.

Exobiopolymer production of Phytocordyceps sp. BCC 2744 and Akanthomyces pistillariiformis BCC 2694; optimization and scale-up

Production of exobiopolymers by Phytocordyceps sp. BCC 2744 and Akanthomyces pistillariiformis BCC 2694, interleukin-8 (IL-8) inducers, were optimized using experimental design. Biological and physiological properties of these exobiopolymers are attractive to use as wound-dressing material, so that it is very interesting to increase its production. Phytocordyceps sp. BCC 2744 and Akanthomyces pistillariiformis BCC 2694 were cultivated on different carbon and nitrogen sources and the best carbon and nitrogen sources for exobiopolymer production of Phytocordyceps sp. BCC 2744 were glucose and peptone, respectively, and 0.88 g/L exobiopolymer was obtained. Higher exobiopolymer (1.82 g/L) was obtained on glucose and meat extract by Akanthomyces pistillariiformis BCC 2694. After the effects of 4 variables were studied using a two-level fractional design, glucose and peptone concentration were the most influential parameters on exobiopolymer production of Phytocordyceps sp. BCC 2744. Lower exobiopolymer production was obtained in the medium supplemented with 5-Fluorouracil and vitamin solution at high level (10 mM and 3mL/L, respectively). The highest exobiopolymer production was obtained on 60 g/L glucose and 20 g/L peptone and 2.32 g/L exobiopolymer was produced. About 4.0 g/L exobiopolymer production in a 20 L bioreactor was obtained. At least 4 variables; medium type, nitrogen sources, glucose, and nitrogen concentration were applied on a two-level factorial design of biomass and exobiopolymer production of Akanthomyces pistillariiformis BCC 2694. Models obtained from the multiple regression are significant. At high level of glucose (60 g/L), phosphate medium, and 20 g/L meat extract, higher exobiopolymer production and about 2.54 g/L was obtained. About 4.5 g/L exobiopolymer production in 20 L bioreactor was obtained.

Expression and Secretion of Endostar Protein by Escherichia Coli: Optimization of Culture Conditions Using the Response Surface Methodology

Endostar as a specific drug in treatment of the nonsmall cell lung cancer is produced using Escherichia coli expression system. Plackett-Burman design (PBD) and response surface methodology (RSM) are statistical tools for experimental design and optimization of biotechnological processes. This investigation aimed to predict and develop the optimal culture condition and its components for expression and secretion of endostar into the culture medium of E. coli. The synthetic endostar coding sequence was fused with PhoA signal peptide. The nine factors involved in the production of recombinant protein-postinduction temperature, cell density, rotation speed, postinduction time, concentration of glycerol, IPTG, peptone, glycine, and triton X-100-were evaluated using PBD. Four significant factors were selected based on PBD results for optimizing culture condition using RSM. Endostar was purified using cation exchange chromatography and size exclusion chromatography. The maximum level of endostar was obtained under the following condition: 13.57-h postinduction time, 0.76% glycine, 0.7% triton X-100, and 4.87% glycerol. The predicted levels of endostar was significantly correlated with experimental levels (R 2=0.982, P=0.00). The obtained results indicated that PBD and RSM are effective tools for optimization of culture condition and its components for endostar production in E. coli. The most important factors in the enhancement of the protein production are glycerol, glycine, and postinduction time.

Optimization of the fermentation process of Cordyceps sobolifera Se-CEPS and its anti-tumor activity in vivo.

BackgroundCordyceps sobolifera (C. sobolifera) isolated from cicadae was used as the starting fungus to produce selenium-enriched C. sobolifera extracellular polysaccharide (Se-CEPS). An orthogonal experimental design based on a single-factor experiment was used to optimize the C. sobolifera fermentation conditions, including the potato juice, peptone, and KH2PO4 concentrations. Ultraviolet (UV) and infrared (IR) analyses of CEPS and Se-CEPS were conducted, as well as an in vivo anti-tumor analysis.ResultsUnder optimal conditions (i.e., 40 potato juice, 0.4 KH2PO4, and 0.5 % peptone), the fermentation yield of Se-CEPS was 5.64 g/L. UV and IR spectra showed that Se-CEPS contained a characteristic absorption peak of a selenite Se = O double bond, demonstrating the successful preparation of Se-CEPS. Activity tests showed that Se-CEPS improved the immune organ index, serum cytokine content, and CD8+ and CD4+ T lymphocyte ratio in colon cancer CT26 tumor-bearing mice, thereby inhibiting tumor growth. When combined with 5-FU, Se-CEPS reduced the toxicity and enhanced the function of 5-FU.ConclusionThe result of these experiments indicated that orthogonal experimental design is a promising method for the optimization of Se-CEPS production, and the Se-CEPS from C. sobolifera can improve the anti-tumor capacity of mice.Electronic supplementary materialThe online version of this article (doi:10.1186/s13036-016-0029-0) contains supplementary material, which is available to authorized users.

Detoxification of Groundnut Cake Naturally Contaminated with Aflatoxin B1 Using Rhodococcus erythropolis in Shake Flask Bioreactors

Degradation of aflatoxin B1 in groundnut cake, a residue after oil extraction, by Rhodococcus erythropolis was optimized using response surface methodology. The bacterium was first grown in synthetic medium to determine optimal growth conditions using the combination of the Plackett–Burman and Box–Behnken methods and consequently aflatoxin B1 in groundnut cake slurry was degraded under varying culture conditions. Optimal growth conditions were found as 22.5 °C of temperature, pH 7, 100 mL of culture volume in 500 mL flasks, 1 % (v/v) of inoculum size, 135 rpm of agitation speed, 5 g/L of glucose and 5 g/L of peptone concentration according to analysis of the Box–Behnken design. Optimal detoxification conditions were found as 27.4 % (w/v) of solid concentration, 4.88 % (v/v) of inoculum size and 24 h of incubation time by Box–Behnken response surface optimization. Maximum detoxification level was predicted as 92.2 % by the constructed model while the experimental counterpart was 87.3 %. The suggested culture conditions have the potential to decrease aflatoxin B1 from 200 μg/kg to below 20 μg/kg, the regulatory limit, in feed materials. Further studies are needed to test the obtained results at a larger scale and to finalize safety assessment of the final product by animal testing.

Biodegradation of 4-chlorophenol in an airlift inner loop bioreactor with mixed consortium: effect of HRT, loading rate and biogenic substrate.

In the present work, removal of 4-chlorophenol (4-CP) by the mixed microbial consortium was evaluated in an airlift inner loop bioreactor. During the study, the effect of various reactor parameters such as hydraulic retention time (HRT), biogenetic substrate concentration, loading rate, and initial substrate concentration on the removal efficiency of 4-CP was investigated. Bioreactor showed a maximum removal rate of 16.59 mg/L/h at the optimum conditions of 24 h HRT, 400 mg/L initial 4-CP, and 0.2 g/L peptone. The optimum HRT found was 24 h after that the washout occured, and the degradation efficiency almost dropped to 50 % at 18 h HRT. Effect of peptone showed that lower concentration of peptone improves 4-CP removal efficiency of the bioreactor. Also, the mixed consortium had utilized 4-CP as a carbon source, as evidenced by the increasing biomass concentration with 4-CP at constant peptone concentration. The presence of 5-chloro 2-hydroxymuconic semialdehyde in the reactor infers that the mixed consortium has followed the meta-cleavage pathway for 4-CP degradation.

Novel Bacillus subtilis IND19 cell factory for the simultaneous production of carboxy methyl cellulase and protease using cow dung substrate in solid-substrate fermentation.

BackgroundHydrolytic enzymes, such as cellulases and proteases, have various applications, including bioethanol production, extraction of fruit and vegetable juice, detergent formulation, and leather processing. Solid-substrate fermentation has been an emerging method to utilize low-cost agricultural residues for the production of these enzymes. Although the production of carboxy methyl cellulase (CMCase) and protease in solid state fermentation (SSF) have been studied extensively, research investigating multienzyme production in a single fermentation process is limited. The production of multienzymes from a single fermentation system could reduce the overall production cost of enzymes. In order to achieve enhanced production of enzymes, the response surface methodology (RSM) was applied.ResultsBacillus subtilis IND19 utilized cow dung substrates for the production of CMCase and protease. A central composite design and a RSM were used to determine the optimal concentrations of peptone, NaH2PO4, and medium pH. Maximum productions of CMCase and protease were observed at 0.9 % peptone, 0.78 % NaH2PO4, and medium pH of 8.41, and 1 % peptone, 0.72 % NaH2PO4, and medium pH of 8.11, respectively. Under the optimized conditions, the experimental yield of CMCase and protease reached 473.01 and 4643 U/g, which were notably close to the predicted response (485.05 and 4710 U/g). These findings corresponded to an overall increase of 2.1- and 2.5-fold in CMCase and protease productions, respectively.ConclusionsUtilization of cow dung for the production of enzymes is critical to producing multienzymes in a single fermentation step. Cow dung is available in large quantity throughout the year. This report is the first to describe simultaneous production of CMCase and protease using cow dung. This substrate could be directly used as the culture medium without any pretreatment for the production of these enzymes at an industrial scale.

Bioconcentration of perfluoroalkyl substances by Chironomus plumosus larvae in water with different types of dissolved organic matters

The effects of four types of dissolved organic matters (DOM) on the bioconcentration of perfluoroalkyl substances (PFASs) in Chironomus plumosus larvae have been studied. The PFASs included perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), and perfluorododecanoic acid (PFDoA). The DOM included humic acid (HA), fulvic acid (FA), tannic acid (TA), and a protein, peptone (PEP), and their concentrations ranged from 0 to 50 mg L−1. The results showed that, upon bioconcentration equilibrium, the body burdens of longer perfluoroalkyl chain PFASs (PFOS, PFDA, PFUnA and PFDoA) decreased with PEP and HA concentrations while increased with FA and TA concentrations. When FA and TA concentrations increased from 0 to 50 mg L−1, body burdens of these PFASs increased by 7.5%–148.8% and 5.7%–37.1%, respectively. However, the DOM had no significant impact on the body burdens of shorter perfluoroalkyl chain PFASs (PFOA and PFNA). All of the four types of DOM lowered not only the uptake rate constants (ku) of PFASs due to the decrease of freely dissolved PFAS concentrations, but also the elimination rate constants (ke) due to the inhibition effect of DOM on the PFAS elimination from the larvae. The reduction in the two constants varied with both DOM and PFAS types. In the presence of PEP and HA with larger molecular weights, the ku values decreased more than ke, leading to the decreased body burdens of longer perfluoroalkyl chain PFASs. As for FA and TA with smaller molecular weights, the ke values decreased more than ku, resulting in increased body burdens of longer perfluoroalkyl chain PFASs. This study suggests that the effects of DOM on PFAS bioconcentration depend not only on the concentration but also on the molecule weight of DOM, which should be considered in the bioavailability assessment of PFASs.

The effect of peptone on the structure of electrodeposited Sn-Fe binary alloys

Sn-Fe thin films were electrodeposited by constant current deposition on copper substrates using an aqueous gluconate based electrolyte with varying concentrations of the organic additive peptone. Good quality metallic deposits were obtained with surface morphologies which varied with the concentration of peptone present in the electrolyte. The effect of peptone concentration on the deposition process was studied using electrochemical polarization curves and EDX analysis. The effect of peptone concentration on deposit structure and surface morphology was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and 57Fe and 119Sn conversion electron Mossbauer spectroscopy (CEMS). It was concluded that the addition of small amounts of peptone to the electrolyte slightly increased the bath stability and led to changes in the alloy composition of the electrodeposits. It was found that increases in the peptone content increased the amount of the crystalline structure in the deposits with corresponding reductions in the amounts of amorphous structure present in the deposits.

Influence of Dissolved Organic Matter on Sorption and Desorption of 1,2,4-trichlorobenzene and 1,2,4,5-tetrachlorobenzene onto Wood Char

ABSTRACTSorption and desorption of 1, 2, 3-trichlorobenzene (TCB) and 1,2,4,5-tetrachlorobenzene (TeCB) onto wood char prepared from maple wood shavings heated at 500°C were studied in the presence of dissolved organic matter (DOM), including humic acid (HA), L-malic acid (L-MA), and peptone. Compared to TCB, TeCB exhibited more nonlinear and stronger sorption onto wood char. Nonlinearity of the sorption isotherms increased in the presence of DOM. The presence of HA enhanced the sorption capacity and desorption hysteresis of TCB and TeCB on wood char mainly due to the strong sorption of HA on wood char surface. Moreover, there were positive relations between Kd values of TCB and TeCB and the HA concentration (p < 0.01). In contrast, peptone reduced the sorption capacity and increased the sorption reversibility because of the partition of TCB and TeCB in peptone solution. L-MA at 50-200 mg·L−1 also leads to a decrease in sorption capacity and irreversibility attributed to solubilization, although the sorbed L-MA on the wood char surface can slightly increase TCB and TeCB sorption. At the same concentration, peptone leads to a higher decrease in TCB sorption than L-MA. Also, negative correlations were found between Kd values of TCB and TeCB and the L-MA and peptone concentration (p < 0.01). Our results may help to understand the different impacts of DOM on the transport and fate of halogenated aromatic hydrocarbons in aquatic environments polluted with chars.

Halotolerant Biofilm in Coffee Beans for Phenanthrene Degradation Under Selected Culture Conditions through a Plackett-Burman Experimental Design

A halotolerant biofilm was developed on green coffee beans by sequential enrichment in the presence of diesel in order to degrade phenanthrene. Experiments were performed under several combined culture conditions using a Plackett-Burman experimental design. The microorganisms composing the biofilm were identified. These included three fungi, Aspergillus niger, Fusarium solani and Fusarium oxysporum, identified by the Fungal Biodiversity Centre of Holland by macroscopic and microscopic morphological evaluation and by molecular techniques (18s-ITS1-5.8SITS2- 28s rRNA); two yeasts, Candida orthopsilosis and Rhodotorula mucilaginosa; and two bacteria, Pseudomonas putida and Klebsiella variicola, identified by the Mexican Collection of Microbial Cultures (Coleccion Mexicana de Cultivos Microbianos, CINVESTAV) according to colony morphology and biochemical [API 20C AUX and API20 (NE and E), respectively] and molecular (fragments ITS1-5.8S-16s-26s and 16s rRNA, respectively) tests. Each microorganism and biofilm were tested for their tolerance to diesel and salinity conditions and their capacity to degrade phenanthrene; degradation capacity was affected significantly (α<0.05) at low concentrations of NaNO3 and KH2 PO4 and at high concentrations of peptone, CaCO3 and FeSO4 (R2=0.95; C=24.97). Two of the tested conditions, T2 and T5, degraded 91.92% and 89.33%, respectively, of 180 mg/L of phenanthrene. Thus, the biofilms developed from microorganisms of green coffee beans preadapted to salinity conditions presented the metabolic capability to remove phenanthrene from seawater under selective culture conditions.

Fermentation optimization of a Saccharomyces cerevisiae strain producing 1F9 recombinant spidroin

The fermentation of a Saccharomyces cerevisiae strain producing recombinant spidroin IF9 was optimized. A simplified two-stage scheme of the process was developed; the effect of sucrose, glucose, fructose, and galactose on the efficiency of the process was investigated. The optimal concentration of sucrose in the medium and replenishment was determined. The influence of peptone, tryptone, and casein hydrolysate of various brands on the effectiveness of the fermentation was analyzed. The optimal concentrations of peptone and yeast extract in the medium and replenishment were determined. As a result, owing to the optimization, the process of fermentation was simplified, a new composition of a complex replenishment was designed, and sucrose-specific consumption was reduced by two times, whereas the expenses of peptone and yeast extract were decreased by about 2.5 times, the yield of biomass per unit of the culture broth volume grew by ∼ 40%, and that of the protein of interest increased by ∼ 60%.

OPTIMASI MEDIA FERMENTASI Aspergillus oryzae, PENGHASIL ANTIJAMUR PATOGEN BUAH KAKAO Phytophthora palmivora Fermentation Medium Optimization of Aspergillus oryzae, Antifungals Producer for Cacao Pathogen Phytophthora palmivora

Indonesia was known as a producer and exporter of cacao, but nowadays Indonesia had an issue in cacao production caused by microorganisms (Phytophtora palmivora) that capable of reducing the amount of cacao production each year. This study follows up a previous study that had found compounds that are actively against at Phytophtora palmivora from Aspergillus oryzae metabolites. In this study the compound will be produced in greater numbers to optimize fermentation medium. The first stage was conducted to determine the profile of the active compound and to analyze the best carbon, nitrogen source for Aspergillus oryzae fermentation medium. The second stage was designed by using Response Surface Method (RSM) with Central Composite Design (CCD) to optimize two variables in the fermentation medium, glucose concentration (the best carbon source) and the concentration of peptone (best nitrogen source). The expected response was the most active compounds percentage of the area. Data analysis was performed by Design Expert DX 7.1.5 program. The first stage of this study presumed that Tenuazonic acid compounds with a molecular weight of 198.1126 gram.mol was an antifungal compound produced by Aspergillus oryzae fungus to prevent Phythopthora palmivora fungus pathogens cacao pods. In addition the results are that glucose was the best carbon source (mean % relative area of antifungal compounds: 85.39%) and that peptone was selected as the best source of nitrogen (mean % relative area of antifungal compounds: 91.07%). The second stage showed the optimum conditions of fermentation medium antifungal Aspergillus oryzae was the composition of glucose 35.25 g/L and peptone 16.7 g/L. The combination of both compositions would yield a mean response of laboratory data % relative area of antifungal compounds 91.2217% and the estimated value (prediction) by Design Expert models 92.2936%. Difference in the estimated values (the response of the model) to the value of the results of response in laboratory experiments at 1.1614%, then it could be concluded that the model used was appropriate and able to explain the applied experimentaldata.-1Kata kunci: Cacao, Aspergillus oryzae, Phytophtora palmivora, active compound, optimization of fermentation medium, Response Surface Method (RSM)

Enhanced D-lactic acid production from renewable resources using engineered Lactobacillus plantarum.

D-lactic acid is used as a monomer in the production of poly-D-lactic acid (PDLA), which is used to form heat-resistant stereocomplex poly-lactic acid. To produce cost-effective D-lactic acid by using all sugars derived from biomass efficiently, xylose-assimilating genes encoding xylose isomerase and xylulokinase were cloned into an L-lactate-deficient strain, Lactobacillus plantarum. The resulting recombinant strain, namely L. plantarum NCIMB 8826 ∆ldhL1-pLEM-xylAB, was able to produce D-lactic acid (at optical purity >99%) from xylose at a yield of 0.53gg(-1). Simultaneous utilization of glucose and xylose to produce D-lactic acid was also achieved by this strain, and 47.2gL(-1) of D-lactic acid was produced from 37.5gL(-1) glucose and 19.7gL(-1) xylose. Corn stover and soybean meal extract (SBME) were evaluated as cost-effective medium components for D-lactic acid production. Optimization of medium composition using response surface methodology resulted in 30% reduction in enzyme loading and 70% reduction in peptone concentration. In addition, we successfully demonstrated D-lactic acid fermentation from corn stover and SBME in a fed-batch fermentation, which yielded 61.4gL(-1) D-lactic acid with an overall yield of 0.77gg(-1). All these approaches are geared to attaining high D-lactic acid production from biomass sugars to produce low-cost, highly thermostable biodegradable plastics.

Application of Response Surface Methodology for Xanthan Gum and Biomass Production Using Xan-thomonas campestris

Xanthan gum is an extracellular polysaccharide produced by various Xanthomonas species such as X. campestris. The objective of present study was to investigate the influence of different carbon and nitrogen sources on xanthan gum production by X. campestris. Using an ex- perimental Response Surface Methodology (RSM) complemented with a Central Composite De- sign (CCD), the impact of peptone, lactose, glucose and ammonium nitrate in medium were esti- mated for their individual and interactive effects on biomass and xanthan gum production. The optimal concentrations of peptone, lactose, glucose and ammonium nitrate for xanthan gum yield and biomass production was determined as 9.25 g/l, 53.37 mmol, 29.31 mmol and 4.58 g/l for xan- than gum yield and 6.77 g/l, 52.65 mmol, 38.12 mmol and 3.54 g/l for biomass production. Under the optimum experimental conditions, the xanthan gum yield reached to its maximum value (8.42 g/l). The results provide the support data for xanthan gum production on a large scale.

Enhancing inulinase yield by irradiation mutation associated with optimization of culture conditions.

A new inulinase-producing strain was isolated from rhizosphere soils of Jerusalem artichoke collected from Shihezi (Xinjiang, China) using Jerusalem artichoke power (JAP) as sole carbon source. It was identified as an Aspergillus niger strain by analysis of 16S rRNA. To improve inulinase production, this fungus was subjected to mutagenesis induced by 60Co γ-irradiation. A genetically stable mutant (designated E12) was obtained and it showed 2.7-fold higher inulinase activity (128 U/mL) than the parental strain in the supernatant of a submerged culture. Sequential methodology was used to optimize the inulinase production of stain E12. A screening trial was first performed using Plackett-Burman design and variables with statistically significant effects on inulinase bio-production were identified. These significant factors were further optimized by central composite design experiments and response surface methodology. Finally, it was found that the maximum inulinase production (185 U/mL) could be achieved under the optimized conditions namely pH 7.0, yeast extract concentration of 5.0 g/L, JAP concentration of 66.5 g/L, peptone concentration of 29.1 g/L, solution volume of 49.4 mL in 250-mL shake flasks, agitation speed of 180 rpm, and fermentation time of 60 h. The yield of inulinase under optimized culture conditions was approximately 1.4-fold of that obtained by using basal culture medium. These findings are of significance for the potential industrial application of the mutant E12.