Initial Medium pH Research Articles

Production and Characteristics of a Bioflocculant by Klebsiella pneumoniae YZ-6 Isolated from Human Saliva

The production and characterization of a bioflocculant, MBF-6, by Klebsiella pneumoniae was investigated. Optimum culture conditions for bioflocculant production were an initial medium pH of 7, an incubation temperature of 30 °C, and an inoculum size of 1% (v/v) of cell density 1.0 × 10(8) cfu/mL. The carbon, nitrogen, and cation sources for optimum bioflocculant production were glucose, peptone, and ZnCl₂. The bioflocculant mainly consisted of protein (3.4%) and sugar (95.1%). Fourier transform infrared (FTIR) spectrum revealed the presence of carboxyl and hydroxyl groups while the thermogravimetric analysis (TGA) showed a degradation temperature (T(d)) of 81.4 °C. MBF-6 had a good flocculating rate in kaolin suspension without cation addition and was stable over a wide range of pH and temperature. Investigation on the flocculation efficacy of the characterized MBF-6 for wastewater treatment of dairy, woolen, brewery, and sugar industries suggested it to be effective.

PRODUCTION OF NARINGINASE FROM A NEW SOIL ISOLATE, Bacillus methylotrophicus: ISOLATION, OPTIMIZATION AND SCALE-UP STUDIES

Five strains of naringin-degrading bacteria were isolated and found to be positive for extracellular naringinase activity. The one that showed highest activity in the selective medium was identified by 16S rRNA analysis as Bacillus methylotrophicus. The best combination of carbon–nitrogen source was determined by employing two-level full factorial analyses, comprising 24 experiments in shake flasks. Sucrose–yeast extract showed significant increase in naringinase activity (7.46 U/L) compared to the basal medium. Naringinase production was found to be inducible and naringin was found to be the best inducer among naringin, naringenin, hesperidin, and L-rhamnose. Inoculum size of 2% (v/v) and age of 48 hr favored naringinase and biomass production. Highest naringinase activity of 8 U/L was observed at the initial medium pH of 6. Response surface modeling was applied based on central composite design to determine the effects of three independent variables (sucrose, yeast extract, and naringin) and their mutual interactions. In total, 20 experiments were conducted and a statistical model was developed, which predicted naringinase production of 10.61 U/L. Subsequently, verification experiments were conducted and validity of the model was verified. Bioreactor studies conducted with the optimized medium showed an enzyme production of 12.05 U/L within 34 hr of fermentation.

English

Soft rot disease of Amorphorallus konjac, an important and potentially destructive corms disease, is caused by Pectobacterium species. Now, the conventional methods of controlling the disease include the breeding variety and the chemical control, but the effects are uncomfortable. The aim of this study was to screen antagonistic bacteria for soft rot disease and optimize its fermentation conditions. The antagonistic bacterium (strain C12) confirmed Bacillus subtilis by the identification of Biolog system and analysis of 16S rDNA gene sequence. Antimicrobial spectrum of the strain C12 was determined by growth rate method, which could restrain the growth of 12 pathogens. The fermentation conditions of the strain C12 were studied by using the single-factor method. The optimal fermentation conditions for antagonistic bacteria were as follow: Medium initial pH 7.0, the fermentation temperature 31°C, the quantity of medium 50 mL in a 250 mL flask, the inoculation volume 2.5%, the incubation time 22 h and the rotation speed 180 rpm, the glucose as carbon source and yeast as nitrogen source. The fermentation liquor of the strain C12 was twice than the streptomycin in control effect of pot experiment. The research provides reference for controlling soft rot disease of A. konjac. The findings suggested that the strain C12 could be exploited as a biocontrol agent for soft rot pathogens.   Key words: Soft rot disease, antagonistic bacteria, characterization, fermentation condition, optimization.

Intensification of sonochemical degradation of ammonium perfluorooctanoate by persulfate oxidant

Ammonium perfluorooctanoate (APFO) is an emerging environmental pollutant attracting significant attention due to its global distribution, high persistence, and bioaccumulation properties. The decomposition of APFO in aqueous solution with a combination of persulfate oxidant and ultrasonic irradiation was investigated. The effects of operating parameters, such as ultrasonic power, persulfate concentration, APFO concentration, and initial media pH on APFO degradation were discussed. In the absence of persulfate, 35.5% of initial APFO in 46.4μmol/L solution under ultrasound irradiation, was decomposed rapidly after 120min with the defluorination ratio reaching 6.73%. In contrast, when 10mmol/L persulfate was used, 51.2% of initial APFO (46.4μmol/L) was decomposed and the defluorination ratio reached 11.15% within 120min reaction time. Enhancement of the decomposition of APFO can be explained by acceleration of substrate decarboxylation, induced by sulfate radical anions formed from the persulfate during ultrasonic irradiation. The SO4−•/APFO reactions at the bubble-water interface appear to be the primary pathway for the sonochemical degradation of the perfluorinated surfactants.

Effect of Some Environmental Parameters on Biobutanol Production by Clostridium acetobutylicum NCIMB 13357 in Date Fruit Medium

Date fruit juice contains high concentration of simple sugars ranging from 65 to 75% (w/w) in dry form. In this study, the potential of date fruit juice as biobutanol fermentation medium by C. acetobutylicum was investigated. The fermentation process was carried out at initial pH of 5, 6 and 7, incubation temperature of 30, 35 and 40 degrees C for 72 hours. The date fruit concentrations tested were 10, 20, 30 and 40 g L(-1). Medium containing 30 g L(-1) of date fruit at 35 degrees C incubation temperature with initial medium pH 7.0 gave the highest concentration of solvents of 3.1, 0.1 and 1.1 g L(-1) butanol, ethanol and acetone respectively. The yield and productivity of biobutanol were 0.32 g g(-1) and 0.044 g L(-1)/h respectively, while for total ABE were 0.45 g g(-1) and 0.06 g L(-1) h, respectively.

Response Surface Methodology Based Optimization of β-Glucosidase Production from Pichia pastoris

The thermotolerant yeast Pichia etchellsii produces multiple cell bound β-glucosidases that can be used for synthesis of important alkyl- and aryl-glucosides. Present work focuses on enhancement of β-glucosidase I (BGLI) production in Pichia pastoris. In the first step, one-factor-at-a-time experimentation was used to investigate the effect of aeration, antifoam addition, casamino acid addition, medium pH, methanol concentration, and mixed feed components on BGLI production. Among these, initial medium pH, methanol concentration, and mixed feed in the induction phase were found to affect BGLI production. A 3.3-fold improvement in β-glucosidase expression was obtained at pH 7.5 as compared to pH 6.0 on induction with 1 % methanol. Addition of sorbitol, a non-repressing substrate, led to further enhancement in β-glucosidase production by 1.4-fold at pH 7.5. These factors were optimized with response surface methodology using Box-Behnken design. Empirical model obtained was used to define the optimum "operating space" for fermentation which was a pH of 7.5, methanol concentration of 1.29 %, and sorbitol concentration of 1.28 %. Interaction of pH and sorbitol had maximum effect leading to the production of 4,400 IU/L. The conditions were validated in a 3-L bioreactor with accumulation of 88 g/L biomass and 2,560 IU/L β-glucosidase activity.

Production of Avermectin B1b From Streptomyces avermitilis 41445 by Batch Submerged Fermentation

Background: Avermectin B1b, a component of commercially available abamectin is obtained as fermentation product of Streptomyces avermitilis and has frequently been used as anthelmintic and insecticidal agent. Secondary metabolite production, avermectin B1b in present study, is dependent on medium composition therefore a proper medium should be designed for the fermentation process in order to have the best production. Objectives: The main objective of this study was the selection and optimization of medium for maximum production of avermectin B1b from S. avermitilis 41445. Materials and Methods: Eight different growth media were used for the production of avermectin B1b. Results: However the maximum production of avermectin B1b (17 mg/L) was obtained by using SM2 growth medium containing soluble corn starch, yeast extract, KCl, CaCO3 and MgSO4 which was detected qualitatively by using TLC and quantitatively by HPLC. Conclusions: Maximum production was observed with initial medium pH of 7, 10% inoculum size with incubation temperature of 31°C for 10 days of fermentation period.

Optimization of carboxymethylcellulase production from Bacillus amyloliquefaciens SS35.

In this paper, we have attempted optimization of production of enzyme carboxymethylcellulase or endoglucanase from the bacterium Bacillus amyloliquefaciens SS35. Optimization has been carried out in two stages using statistical experimental design, viz. medium optimization and optimization of fermentation parameters. For medium optimization, Plackett–Burman design followed by central composite design (CCD) was used, while for optimization of fermentation parameters one-variable-at-a-time method followed by CCD was used. Carbon and nitrogen sources in the medium have been revealed to be the significant factors for enzyme production (carboxymethylcellulose 18.05 g/L; yeast extract 8 g/L and peptone 2 g/L). The inorganic salts have been found to be insignificant components of medium. Optimum fermentation parameters for optimized medium were: initial medium pH 5.65, incubation temperature = 40 °C, shaking speed = 120 rpm, and inoculum size = 6.96 %, v/v. Interestingly, the influence of all four parameters was almost independent with no interlinks. Secondly, the overall effect of all parameters was also low, as indicated by linear, square and interaction regression coefficients that were at least one order of magnitude lower than the intercept in the model equation. These results essentially meant that medium components dominate overall enzyme production process in comparison to fermentation parameters.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-013-0169-6) contains supplementary material, which is available to authorized users.

Growth and Fermentation Characteristics of Saccharomyces cerevisiae NK28 Isolated from Kiwi Fruit

The influences of glucose concentration, initial medium acidity (pH), and temperature on the growth and ethanol production of Saccharomyces cerevisiae NK28, which was isolated from kiwi fruit, were examined in shake flask cultures. The optimal glucose concentration, initial medium pH, and temperature for ethanol production were 200 g/l, pH 6.0, and 35oC, respectively. Under this growth condition, S. cerevisiae NK28 produced 98.9 ± 5.67 g/l ethanol in 24 h with a volumetric ethanol production rate of 4.12 ± 0.24 g/l·h. S. cerevisiae NK28 was more tolerant to heat and ethanol than laboratory strain S. cerevisiae BY4742, and its tolerance to ethanol and fermentation inhibitors was comparable to that of an ethanologen, S. cerevisiae D5A.

Studies of Soybean Peptides by Solid-State Fermentation with Multi-Strains

In this paper, the condition of aspergillus niger and the bacillus subtilis mixing fermentation to produce soybean peptides was studied. The results indicated that the best fermentation condition of the aspergillus niger and the bacillus subtilis mixing fermentation to produce soybean peptides is that: the initial pH of the culture medium is 8.0, the proportion of mixture strains (aspergillus niger vs bacillus subtilis) is 2 to 1,the fermentation temperature is 30°C and the fermentation time is 80 hours. In this condition the degree of hydrolysis of the fermentation bean pulp is 36.5%.

New generation ion-imprinted nanocarrier for removal of Cr(VI) from wastewater

The purpose of this study was to prepare a novel ion-imprinted nanoparticle to remove Cr(VI) ions from waste water. For this, Cr(VI) ions were complexed with 2-methacryloylamido histidine (MAH) and then Cr(VI)-imprinted poly(HEMAH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique. The templates, Cr(VI) ions, were removed from the nanoparticles using 0.1 M of HNO3 solution. The specific surface area of the Cr(VI)-imprinted poly(HEMAH) nanoparticles was found to be 1,397.85 m2/g, and the particle size was calculated as 155.3 nm. These Cr(VI)-imprinted nanoparticles were used for the adsorption/desorption of Cr(VI) ions from its aqueous solutions. The effects of initial Cr(VI) concentration and medium pH on the Cr(VI) adsorption capacity were also studied. The maximum adsorbed amount of Cr(VI) on the imprinted nanoparticles was found to be 3,830.58 mg/g nanoparticle in pH 4.0. In order to investigate the selectivity of the imprinted nanoparticle, adsorption studies were repeated using Cr(III) ions. The selectivity results demonstrated that Cr(VI)-imprinted poly(HEMAH) nanoparticles showed high affinity for the Cr(VI) ions than Cr(III). The Cr(VI)-imprinted nanoparticles were used several times without decreasing their Cr(VI) adsorption capacities.

Enhanced tannase production by Bacillus subtilis PAB2 with concomitant antioxidant production

Abstract The present study was aimed at finding the optimal conditions for tannin biodegradation by Bacillus subtilis PAB2, a newly isolated soil bacterium, and to study its fermentative byproducts. Tannase production by B. subtilis PAB2 in optimum level was studied by one variable at a time (OVAT) approach followed by Box–Behnken response surface methodology (RSM) using six important variables. The maximum tannase production (10.69 U/ml) was achieved in the presence of 0.47% (w/v) tannic acid, 0.23% (w/v) ammonium chloride (NH 4 Cl), 0.1% (w/v) potassium dihydrogen phosphate (KH 2 PO 4 ) and 0.046% (w/v) magnesium sulphate (MgSO 4 ) with the initial medium pH of 5.9 and incubation at 34.1 °C for 36 h under shaking condition (120 rpm). An overall 2.06 fold increase in tannase production was achieved after RSM global formulation. One of the major end product of tannin degradation i.e. gallic acid, was accumulated in the highest level (6.45 mg/ml) in 36 h of fermentation. Liquid chromatography and mass spectroscopy results indicated the presence of both gallic acid and pyrogallol in the fermentative end product. Purification of gallic acid and pyrogallol was achieved through high pressure liquid chromatography followed by crystallization and confirmed by Fourier transform infrared spectroscopy. Associated production of tannase as well as gallic acid and pyrogallol by B. subtilis PAB2 makes it obvious in different biotechnological interest.

Removal of cobalt ions from aqueous solutions by using poly(N,N‐dimethylaminopropyl methacrylamide/itaconic acid) hydrogels

ABSTRACTIn this study, N,N‐dimethylaminopropyl methacrylamide (DMAPMAm) homopolymer and DMAPMAm/itaconic acid (DMAPMAm/IA) copolymers were obtained from 60Co‐γ radiation polymerization. Gel fraction and percentage of swelling values were calculated through gravimetrical calculations. In order to increase the swelling of the hydrogel, the amount of IA in initial copolymer composition was gradually increased, but it was observed that gelation values were low. The structural and morphological assessments of homopolymer and copolymers were made by means of several techniques including Fourier Transform Infrared Spectroscopy (FT‐IR), Scanning Electron Microscopy (SEM), and Energy‐Dispersive X‐ray Spectroscopy (EDS). The cobalt ion (Co2+) removal capacities of hydrogel were investigated by taking into account of the initial metal ion concentration and pH of aqueous medium. When it came to the maximum capacity of values obtained from adsorption experiments by using Co2+ solutions at pH 5, they changed between 220 and 245 mg Co2+/g dry hydrogel. FT‐IR, SEM, EDS, and XRD analyses were carried out for enlightening the mechanism of Co2+ removal by hydrogels after the completion of adsorption. Also, desorption studies were conducted using ethylenediaminetetraacetic acid (EDTA). Finally, within approximately 5 days, all adsorbed Co2+ ions were released from hydrogels at pH 5 using 0.1M EDTA solution. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39569.

Microbial production of levanase for specific hydrolysis of levan

A newly isolated bacterial strain from Tunisian thermal source was selected for its ability to produce extracellular levanase when grown on levan substrate. The optimization of carbon source, nitrogen source, temperature and initial pH of the growth medium in submerged liquid cultures were investigated. In fact, levan was found to be a good inducer of levanase enzymes. The optimal temperature and pH of the levanase activity were 40̊C and 6.4, respectively. This enzyme exhibited a remarkable stability and retained 75% of its original activity at 55̊C for more than 1h at pH 6.4. Crude enzyme of the strain rich in levanase was established for the hydrolysis of levan in order to produce fructooligosaccharides with variable degrees of polymerization which could be used in important fields such medicine, food-processing industry and cosmetic. The extracellular levanase of the strain was then, partially purified as determined by SDS-PAGE. The purification was achieved by ammonium sulfate precipitation, gel filtration and DEAE cellulose chromatographies.

English

  A wild strain of Yarrowia lipolytica, identified as LMI 91, was isolated from an oleaginous Brazilian fruit called pequi (Caryocar brasiliense Camb), which is a native species of the Brazilian savannah and which acts as a potent lipase producer. The present study examined the effects of certain factors, such as the combination of casein and meat peptones, as well as the initial pH of a culture medium in lipase produced by Y. lipolytica LMI 91. Experiments were conducted within a low concentration of olive oil, at a temperature of 30°C and a fermentation time of 60 h, under orbital shaking. The response surface methodology was used to determine the optimum concentration of the constituents’ composition. A 22 experimental design with four axial points and three central points was employed in the optimization experiments, and interactive regression analysis was performed to obtain the optimum concentration. The experimental values were found to be in accordance with the predicted values, presenting a correlation coefficient of 0.866. The maximum lipase activity (13.0 U/mL) was obtained by peptone mixture of 70 g/L (1:1) and an initial pH of 5.0.   Key words: Yarrowia lipolytica, wild strain, extracellular lipase, fermentation, optimization.

Physicochemical and sensory qualities of spiced soy-corn milk

A wild strain of Yarrowia lipolytica , identified as LMI 91, was isolated from an oleaginous Brazilian fruit called pequi ( Caryocar brasiliense Camb ), which is a native species of the Brazilian savannah and which acts as a potent lipase producer. The present study examined the effects of certain factors, such as the combination of casein and meat peptones, as well as the initial pH of a culture medium in lipase produced by Y. lipolytica LMI 91. Experiments were conducted within a low concentration of olive oil, at a temperature of 30°C and a fermentation time of 60 h, under orbital shaking. The response surface methodology was used to determine the optimum concentration of the constituents’ composition. A 2 2 experimental design with four axial points and three central points was employed in the optimization experiments, and interactive regression analysis was performed to obtain the optimum concentration. The experimental values were found to be in accordance with the predicted values, presenting a correlation coefficient of 0.866. The maximum lipase activity (13.0 U/mL) was obtained by peptone mixture of 70 g/L (1:1) and an initial pH of 5.0. Keywords : Yarrowia lipolytica , wild strain, extracellular lipase, fermentation, optimization African Journal of Biotechnology Vol. 12(17), pp. 2270-2278

Optimization of novel hyperthermostable β amylase production by Bacillus subtilis DJ5 using solid agroresidual substrates

Eight different low cost starchy agroresidues namely Barley (B), Wheat bran (WB), Sattu (S), Rice powder (RP), Corn flour (CF), Rice husk (RH), Yellow peas split (YPS) and arrowroot (A) were used for solid culturing of Bacillus subtilis DJ5 for production of novel hyperthermostable β amylase. Various process parameters like initial moisture content, inoculum load, medium pH and incubation temperature affecting enzyme production were optimized to ensure maximum enzyme yield. Only 10 % inoculums load and medium pH of 6.9 was found sufficient to achieve maximum enzyme production in all substrates in a decreasing order, B > WB > S > RP > CF > RH > YPS > A. Optimum β amylase production was highly dependent on initial moisture content of substrate as observed from varying requirement of moisture for different substrates. Only 50 % moisture was sufficient for maximum enzyme production of 84.29 U/gdm in CF. For B, RH, YPS, and A 60 % initial moisture resulted in higher production of 120.34, 35.19, 26.59, and 21.58 U/gdm, respectively, at 37 °C. However, for S and RP higher (70 %) moisture content allowed 113.4 and 85.56 U/gdm enzyme production, respectively. Under optimized conditions, maximum β amylase production was observed after 25 h for A, YPS, RH, RP; 41 h for B, WB, CF, and 45 h for S.

Increased alkalotolerant and thermostable ribonuclease (RNase) production from alkaliphilic Streptomyces sp. M49-1 by optimizing the growth conditions using response surface methodology

Total of 171 alkaliphilic actinomycetes were evaluated for extracellular RNase production and Streptomyces sp. M49-1 was selected for further experiments. Fermentation optimization for RNase production was implemented in two steps using response surface methodology with central composite design. In the first step, the effect of independent fermentation variables including temperature, initial pH and process time were investigated. After identification of carbon and nitrogen sources affecting the production by one variable at a time method, concentrations of glucose and yeast extract and also inoculum size were chosen for the second central composite design. A maximum RNase activity was obtained under optimal conditions of 4.14 % glucose concentration, 4.63 % yeast extract concentration, 6.7 × 10⁶ spores as inoculum size for 50 ml medium, 42.9 °C, 91.2 h process time and medium initial pH 9.0. Optimum activity of the enzyme is achieved at pH 11 and temperature 60 °C. The enzyme is highly stable at pH range 9.0-12.0 and at 90 °C after 2 h. Statistical optimization experiments provide 2.25 fold increases in the activity of alkalotolerant and thermostable RNase and shortened the fermentation time compared to that of unoptimized condition. The members of Streptomyces can be promising qualified RNase producer for pharmaceutical industries.

Characterization of an Exopolymeric Flocculant Produced by a Brachybacterium sp.

We evaluated the bioflocculant production potential of an Actinobacteria, which was isolated from a freshwater environment in the Eastern Cape province of South Africa. 16S rDNA nucleotide sequencing analyses revealed that the actinobacteria belongs to the Brachybacterium genus, and the sequences were deposited in the GenBank as Brachybacterium sp. UFH, with accession number HQ537131. Optimum fermentation conditions for bioflocculant production by the bacteria include an initial medium pH of 7.2, incubation temperature of 30 °C, agitation speed of 160 rpm and an inoculum size of 2% (vol/vol) of cell density 3.0 × 108 CFU/mL. The carbon, nitrogen and cation sources for optimum bioflocculant production were maltose (83% flocculating activity), urea (91.17% flocculating activity) and MgCl2 (91.16% flocculating activity). Optimum bioflocculant production coincided with the logarithmic growth phase of the bacteria, and chemical analyses of the bioflocculant showed 39.4% carbohydrate and 43.7% protein (wt/wt). The mass ratio of neutral sugar, amino sugar and uronic acids was 1.3:0.7:2.2. Fourier transform infrared spectroscopy (FTIR) indicated the presence of carboxyl, hydroxyl and amino groups, amongst others, typical for heteropolysaccharide and glycosaminoglycan polysaccharides. Bioflocculant pyrolysis showed thermal stability at over 600 °C, while scanning electron microscope (SEM) imaging revealed a maze-like structure of interlaced flakes. Its high flocculation activity suggests its suitability for industrial applicability.

Optimizing mixed culture of two acidophiles to improve copper recovery from printed circuit boards (PCBs)

In the previous research, the effects of different addition time and amount of printed circuit boards (PCBs) on cells growth and metals recovery in separated and mixed culture of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans were investigated. This paper aimed to optimize mixed culture of both acidophiles for maximizing PCBs addition amounts and copper leaching percentage simultaneously. Initially, influences of inoculums ratio between two acidophiles on their cells growth were studied. Then, initial medium pH and concentrations of FeSO4·7H2O and elemental sulfur (S0) were optimized by response surface methodology (RSM) to improve copper recovery. Finally, multiple-point PCBs addition was tested to determine maximal amounts. Results showed that with initial inoculums ratio (Af:At) 1:2, pH 1.56, FeSO4·7H2O and S0 at 16.88 and 5.44g/L, and PCBs addition 28.8g/L, copper recovery reached 92.6% after 240h cultivation. It was indicated that copper could be efficiently leached out from increased PCBs addition amount and FeSO4·7H2O was remarkably reduced from 22.1 to 16.88g/L.