Effect of aeration rate on production of xylitol from corncob hemicellulose hydrolysate

The effects of different aeration conditions on xylitol production from corncob hemicellulose hydrolysate by Candida sp. ZU04 were investigated. Batch fermentations were carried out in a 3.7-L fermentor at 30°C, pH5.5, and agitation of 300 rpm. It was found that the two-phase aeration process was more effective than the one-phase aeration process in xylitol production. In the first 24h of the aerobic phase, a high aeration rate was applied, glucose was soon consumed, and biomass increased quickly. In the second fermentation phase, aeration rate was reduced and an improved xylitol yield was obtained. The maximum xylitol yield (0.76 g/g) was obtained with an aeration rate of 1.5 vvm (KLa of 37 h⁻¹) for the first 24 h and 0.3 vvm (KLa of 6 h⁻¹) from 24 to 96 h.     

Xanthan gum production by Xanthomonas campestris w.t. fermentation from chestnut extract

Xanthomonas campestris w.t. was used for production of xanthan gum in fermentations with chestnut flour for the first time. Fermentations were carried out with either chestnut flour or its soluble sugars (33.5%) and starch (53.6%), respectively, at 28°C and 200 rpm at initial pH 7.0 in flasks. The effect of agitation rate (at 200, 400, and 600 rpm) on xanthan gum production was also studied in a 2-L batch reactor. It was found that xanthan production reaches a maximum value of 3.3 g/100 mL at 600 rpm and 28°C at 45 h.     

The Influence of Initial Xylose Concentration, Agitation, and Aeration on Ethanol Production by Pichia stipitis from Rice Straw Hemicellulosic Hydrolysate

Rice straw hemicellulosic hydrolysate was used as fermentation medium for ethanol production by Pichia stipitis NRRL Y-7124. Shaking bath experiments were initially performed aiming to establish the best initial xylose concentration to be used in this bioconversion process. In the sequence, assays were carried out under different agitation (100 to 200 rpm) and aeration (V _flask/V _medium ratio varying from 2.5 to 5.0) conditions, and the influence of these variables on the fermentative parameters values (ethanol yield factor, Y _P/S; cell yield factor, Y _X/S; and ethanol volumetric productivity, Q _P) was investigated through a 2² full-factorial design. Initial xylose concentration of about 50 g/l was the most suitable for the development of this process, since the yeast was able to convert substrate in product with high efficiency. The factorial design assays showed a strong influence of both process variables in all the evaluated responses. The agitation and aeration increase caused a deviation in the yeast metabolism from ethanol to biomass production. The best results (Y _P/S?= 0.37 g/g and Q _P?=?0.39 g/l.h) were found when the lowest aeration (2.5 V _flask/V _medium ratio) and highest agitation (200 rpm) levels were employed. Under this condition, a process efficiency of 72.5% was achieved. These results demonstrated that the establishment of adequate conditions of aeration is of great relevance to improve the ethanol production from xylose by Pichia stipitis, using rice straw hemicellulosic hydrolysate as fermentation medium.     

Biotechnological Utilization of Biodiesel-Derived Glycerol for the Production of Ribonucleotides and Microbial Biomass

Ten yeast strains were evaluated concerning their capabilities to assimilate biodiesel-derived glycerol in batch cultivation. The influence of glycerol concentration, temperature, pH and yeast extract concentration on biomass production was studied for the yeast selected. Further, the effect of agitation on glycerol utilization by the yeast Hansenula anomala was also studied. The yeast H. anomala CCT 2648 showed the highest biomass yield (0.30?g?g^?1) and productivity (0.19?g?L^?1?h^?1). Citric acid, succinic acid, acetic acid and ethanol were found as the main metabolites produced. The increase of yeast extract concentration from 1 to 3?g?L^?1 resulted in high biomass production. The highest biomass concentration (21?g?L^?1), yield (0.45?g?g^?1) and productivity (0.31?g?L^?1?h^?1), as well as ribonucleotide production (13.13?mg?g^?1), were observed at 700?rpm and 0.5?vvm. These results demonstrated that glycerol from biodiesel production process showed to be a feasible substrate for producing biomass and ribonucleotides by yeast species.     

Two-Staged Temperature and Agitation Strategy for the Production of Transglutaminase from a Streptomyces sp. Isolated from Brazilian Soils

Transglutaminase catalyzes the cross-linking reaction between a glutamine residue and a free amine residue of proteins leading to the formation of protein aggregates. In this research, the effects of temperature, agitation, and aeration on the production of transglutaminase in a bench reactor by a newly isolated Streptomyces sp. from Brazilian soils were investigated using a factorial experimental design. The parameters evaluated influenced the enzyme production, and the data showed that the best conditions to enhance cell growth were different from those leading to enhanced transglutaminase production. Thus, a temperature and agitation shift strategy was adopted to increase transglutaminase productivity. The temperature and agitation were first set at 34 °C and 350 rpm, respectively, and after 24 h decreasing to 26 °C and 150 rpm until the end of fermentation. The transglutaminase activity obtained was 2.18 U/mL after 42 h of fermentation, which was twice than that obtained using a constant temperature and agitation fermentation strategy.     

Effect of process parameters on production of a biopolymer by Rhizobium sp.

The production of biopolymers by a Rhizobium strain was studied under batch and bioreactor conditions. The best viscosity levels were obtained under low mannitol concentrations as well as low agitation and aeration conditions. Infrared spectra indicated the presence of chemical groups characteristic of microbially produced biopolymers, including C=O and O-acetyl groups. Thermogravimetric analysis showed the characteristic degradation profiles of the exopolysaccharide produced (T _onset=290°C). The experimental design showed that a low substrate concentration (10.0 g/L), and low aeration (0.2 vvm) and agitation (200 rpm) levels should be used. The maximum yield of the process was a Yp/s (g/g) of 0.19±0.1, obtained under optimized conditions.     

Biopolymer Synthesized by Strains of Xanthomonas sp Isolate from Brazil Using Biodiesel-Waste

The future supplies and usage of glycerol are expected to increase as biodiesel plants increase production, and the output will greatly outpace demand. Biodiesel production has already had a significant impact on the price of refined glycerol. A major concern of glycerol producers is the reduced price of glycerol resulting from the increased production of biodiesel. Some alternative uses for this glycerol that have been investigated are substrates for fermentation process or the production of biosurfactants, fatty acids, biopolymers, and others products. This work had as objective to evaluate two strains of Xanthomonas sp isolate from Brazil for xanthan gum in orbital agitator, analizing the apparent viscosity of aqueous solutions and selecting viscosity. The experiments of xanthan gum production were realized in orbital agitator with 120 rpm agitation, for cells production, and 180rpm, for biopolymer production, under a 28 °C temperature. The rheology of the fermentation broth was analyzed by apparent viscosity and the polymer was recovered with ethanol (1:3, v/v). After its recovery, the productivity evaluation was performed. The productivity were 0.157 and 0.363 gL⁻¹ for C1 and 0.186 and 0.363 gL⁻¹ for C9 to media glycerol or glycerol and sucrose, respectively. The viscosity analysis was performed for aqueous solutions 3%, at 25 °C, the best apparent viscosity was obtained using gum synthesized with glycerol and sucrose (50:50) at 25 °C, 143 mPa.s⁻¹ from Xanthomonas sp C1.     

Process Characterization of hCTLA4Ig Production in Transgenic Rice Cell Cultures Using a 3-L Bioreactor

Most of the technical know-how and experience of bioreactor engineering is applicable to plant cell cultures. In this study, transgenic rice cell cultures using RAmy3D promoter were used for the production of human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig). In process aspect, the rice cells during production phase are strongly influenced by hydrodynamic stresses, such as shear stress and bubble burst. Therefore, the effects of agitation and aeration rates on cell growth and hCTLA4Ig production were investigated in a 3-L multi-bioreactor. By increasing over 240 rpm, the detrimental effects on cell growth and hCTLA4Ig production were observed. At an aeration rate of 0.3 vvm, relative cell viability sharply decreased 2 days earlier than those of lower aeration rates. In addition, it was confirmed that the specific yields and the specific productivity at 0.3 vvm were superior to those values at 0.05 vvm. Overall, higher aeration rate showed the improved hCTLA4Ig production in combination experiment. High aeration rates in general, however, have an undesired effect as excessive aeration was found to negatively affect the quality of hCTLA4Ig. Consequently, the hydrodynamic conditions must be tightly regulated during bioreactor operation in order to enhance hCTLA4Ig productivity and quality in transgenic rice cell cultures.     

Effectiveness of Sal Deoiled Seed Cake as an Inducer for Protease Production from Aeromonas sp. S1 for its Application in Kitchen Wastewater Treatment

The present study is an attempt to demonstrate the feasibility of sal (Shorea robusta) deoiled cake—a forest-based industrial by-product—as a cheaper media supplement for augmented protease production from Aeromonas sp. S1 and application of protease in the treatment of kitchen wastewater. Under optimized conditions, protease production could successfully be enhanced to 5.13-fold (527.5 U mL^?1) on using sal deoiled seed cake extract (SDOCE), as medium additive, compared to an initial production of 102.7 U mL^?1 in its absence. The culture parameters for optimum production of protease were determined to be incubation time (48 h), pH (7.0), SDOCE concentration (3 % (v/v)), inoculum size (0.3–0.6 % (v/v)), and agitation rate (100 rpm). The enzyme was found to have an optimum pH and temperature of 8.0 and 60 °C, respectively. The protease preparation was tested for treatment of organic-laden kitchen wastewater. After 96 h of wastewater treatment under static condition, enzyme preparation was able to reduce 74 % biological oxygen demand, 37 % total suspended solids, and 41 % oil and grease. The higher and improved level of protease obtained using sal deoiled seed cake-based media hence offers a new approach for value addition to this underutilized biomass through industrial enzyme production. The protease produced using this biomass could also be used as pretreatment tool for remediation of organic-rich food wastewater.     

Effect of aeration on lignin peroxidase production by Streptomyces viridosporus T7A

The effect of aeration on lignin peroxidase production by Streptomyces viridosporus T7A was studied in a bench-scale bioreactor using a previously optimized growth medium (0.65% yeast extract and 0.1% corn oil, pH7.0) at 37°C and natural pH. Airflow rates of 0.3, 1.0, and 1.5 vvm and a fixed agitation of 200 rpm were initially studied followed by 1.0 vvm and 200, 300, 400, and 500 rpm. The use of 1.0 vvm and 400 rpm increased enzyme concentration 1.8-fold (100–180 U/L) and process productivity 4.8-fold (1.4–6.7 U/[L·h]) in comparison with the use of 200 rpm and 0.3 vvm. The inexpensive corn oil, used as carbon source, besides its antifoam properties, proved to be nonrepressive for enzyme production.     

Maximization of β-Galactosidase Production: A Simultaneous Investigation of Agitation and Aeration Effects

In this work, the agitation and aeration effects in the maximization of the β-galactosidase production from Kluyveromyces marxianus CCT 7082 were investigated simultaneously, in relation to the volumetric enzyme activity and the productivity, as well as the analysis of the lactose consumption and production of glucose, and galactose of this process. Agitation and aeration effects were studied in a 2 L batch stirred reactor. A central composite design (2² trials plus three central points) was carried out. Agitation speed varied from 200 to 500 rpm and aeration rate from 0.5 to 1.5 vvm. It has been shown in this study that the volumetric enzyme production was strongly influenced by mixing conditions, while aeration was shown to be less significant. Linear models for activity and productivity due to agitation and aeration were obtained. The favorable condition was 500 rpm and 1.5 vvm, which lead to the best production of 17 U mL⁻¹ for enzymatic activity, 1.2 U mL⁻¹ h⁻¹ for productivity in 14 h of process, a cellular concentration of 11 mg mL⁻¹, and a 167.2 h⁻¹ volumetric oxygen transfer coefficient.     

Xanthan Gum Production by <Emphasis Type="Italic">Xanthomonas campestris pv. campestris</Emphasis> IBSBF 1866 and 1867 from Lignocellulosic Agroindustrial Wastes

This study aimed to evaluate the properties of xanthan gum produced by Xanthomonas campestris pv. campestris 1866 and 1867 from lignocellulosic agroindustrial wastes. XG was produced using an orbital shaker in a culture medium containing coconut shell (CS), cocoa husks (CH), or sucrose (S) minimally supplemented with urea and potassium. The XG production results varied between the CS, CH, and S means, and it was higher with the CH in strains 1866 (4.48 g L^?1) and 1867 (3.89 g L^?1). However, there was more apparent viscosity in the S gum (181.88 mPas) and the CS gum (112.06 mPas) for both 1866 and 1867, respectively. The ability of XG_CS and XG_CH to emulsify different vegetable oils was similar to the ability of XG_S. All gums exhibited good thermal stability and marked groups in the elucidation of compounds and particles with rough surfaces.     

Siderophore Production by Bacillus megaterium: Effect of Growth Phase and Cultural Conditions

Siderophore production by Bacillus megaterium was detected, in an iron-deficient culture medium, during the exponential growth phase, prior to the sporulation, in the presence of glucose; these results suggested that the onset of siderophore production did not require glucose depletion and was not related with the sporulation. The siderophore production by B. megaterium was affected by the carbon source used. The growth on glycerol promoted the very high siderophore production (1,182 μmol g^?1 dry weight biomass); the opposite effect was observed in the presence of mannose (251 μmol g^?1 dry weight biomass). The growth in the presence of fructose, galactose, glucose, lactose, maltose or sucrose, originated similar concentrations of siderophore (546–842 μmol g^?1 dry weight biomass). Aeration had a positive effect on the production of siderophore. Incubation of B. megaterium under static conditions delayed and reduced the growth and the production of siderophore, compared with the incubation in stirred conditions.     

Optimised isolation of polysaccharides from Lentinula edodes strain NCBI JX915793 using response surface methodology and their antibacterial activities

Mycelial growth in a defined medium by submerged fermentation is a rapid and alternative method for obtaining fungal biomass of consistent quality. Biomass, exopolysaccharides (EPS) and intracellular polysaccharides (IPS) production were optimised by response surface methodology in Lentinula edodes strain LeS (NCBI JX915793). The optimised conditions were pH 5.0, temperature 26°C, incubation period of 25 days and agitation rate of 52 r/min for L. edodes strain LeS. Under the calculated optimal culture conditions, biomass production (5.88 mg mL^? 1), EPS production (0.40 mg mL^? 1) and IPS production (12.45 mg g^? 1) were in agreement with the predicted values for biomass (5.93 mg mL^? 1), EPS (0.55 mg mL^? 1) and IPS production (12.64 mg g^? 1). Crude lentinan exhibited highest antibacterial effects followed by alcoholic, crude and aqueous extracts. The results obtained may be useful for highly effective yield of biomass and bioactive metabolites.     

A Comparison Between Shaker and Bioreactor Performance Based on the Kinetic Parameters of Xanthan Gum Production

Xanthan gum production was studied using sugarcane broth as the raw material and batch fermentation by Xanthomonas campestris pv. campestris NRRL B-1459. The purpose of this study was to optimize the variables of sucrose, yeast extract, and ammonium nitrate concentrations and to determine the kinetic parameters of this bioreaction under optimized conditions. The effects of yeast extract and ammonium nitrate concentrations for a given sucrose concentration (12.1–37.8 g L^?1) were evaluated by central composite design to maximize the conversion efficiency. In a bioreactor, the maximum conversion efficiency was achieved using 27.0 g L^?1 sucrose, 2.7 g L^?1 yeast extract, and 0.9 g L^?1 NH₄NO₃. This point was assayed in a shaker and in a bioreactor to compare bioreaction parameters. These parameters were estimated by the unstructured kinetic model of Weiss and Ollis (Biotechnol Bioeng 22:859–873, 1980) to determinate the yields (Y _P/S), the maximum growth specific rate (μ _max), and the saturation cellular concentration (X*). The parameters of the model (μ _max, X*, m, λ, α, and β) were obtained by nonlinear regression. For production of xanthan gum in a shaker, the values of μ _max and Y _P/S obtained were 0.119 h^?1 and 0.34 g g^?1, respectively, while in a bioreactor, they were 0.411 h^?1 and 0.63 g g^?1, respectively.     

Preliminary kinetic characterization of xylose reductase and xylitol dehydrogenase extracted from Candida guilliermondii FTI 20037 cultivated in sugarcane bagasse hydrolysate for xylitol production

Candida guilliermondii FTI 20037 was cultured in sugarcane bagasse hydrolysate supplemented with 2.0 g/L of (NH₄)₂SO₄, 0.1 g/L of CaCl₂·2H₂O, and 20.0 g/L of rice bran at 35°C; pH 4.0; agitation of 300 rpm; and aeration of 0.4, 0.6, or 0.8 vvm. The high xylitol production (20.0 g/L) and xylose reductase (XR) activity (658.8 U/mg of protein) occurred at an aeration of 0.4 vvm. Under this condition, the xylitol dehydrogenase (XD) activity was low. The apparent K _M for XR and XD against substrates and cofactors were as follows: for XR, 6.4×10⁻² M (xylose) and 9.5×10⁻³ mM (NADPH); for XD, 1.6×10⁻¹ M (xylitol) and 9.9×10⁻² mM (NAD+). Because XR requires about 10-fold less xylose and cofactor than XD for the condition in which the reaction rate is half of the V _max, some interference on the overall xylitol production by the yeast could be expected.     

Investigating the influence of pH,temperature and agitation speed on yellow pigment production by Penicillium aculeatum ATCC 10409

In this study, the combined effect of pH, temperature and agitation speed on yellow pigment production and mycelial growth of Penicillium aculeatum ATCC 10409 was investigated in whey media. Different pH levels (5, 6.5 and 8), temperatures (25, 30 and 35°C) and agitation speed levels (100 and 150 rpm) were tested to determine the best conditions to produce a fungal yellow pigment under submerged fermentation. The best production of yellow pigment (1.38 g/L) was obtained with a pH value of 6.5, a temperature of 30°C and an agitation speed of 150 rpm. In contrast, the maximal biomass concentration (11.12 g/L) was obtained at pH value of 8, a temperature of 30°C and an agitation speed of 100 rpm. These results demonstrated that biomass and yellow pigment production were not directly associated. The identification of the structure of unknown P. aculeatum yellow pigment was detected using UV absorption spectrum and FT-IR spectroscopy.     

Biosorption of strontium from aqueous solutions onto spent coffee grounds

A set of experiments was carried out to evaluate the strontium uptake potential of spent coffee grounds (SCG) by batch tests in aqueous medium. Adsorption of Sr²⁺ as a function of contact time and adsorbent dose, pH, particles size, agitation speed, temperature and co-ions presence was investigated. Obtained results revealed that the maximum adsorption took place at pH range of 5–8 and temperature values between 283 and 333 K. Particles size effect was not very significant and agitation speed influenced on the equilibrium time. Competitive adsorption experiments allowed us to classify the negative effect on the Sr²⁺ uptake according to this order Al³⁺ ? Co²⁺ > Mg²⁺ > Ca²⁺ ? Na⁺ > K⁺ > Cs⁺. Kinetic study indicated that the Sr²⁺ uptake was fast and it was well fitted by the pseudo second order reaction model. Adsorption isotherm was well interpreted by Langmuir model. The maximum adsorption capacity was found to be 69.01 mg g^?1 at pH 7, 293 K, particles sizes = 200–400 μm and agitation speed 250 rpm. The thermodynamic study revealed that the process was spontaneous (ΔG ⁰ < 0), exothermic (ΔH ⁰ < 0) with a raised affinity for Sr²⁺ (ΔG ⁰ < 0, ΔS ⁰ > 0) and occurred by physical adsorption (E _a = 8.37 kJ mol^?1). FTIR analysis showed carboxylic acid and amino group presence on SCG surface playing a vital role in Sr²⁺ biosorption.     

Emulsifying,Flocculating, and Physicochemical Properties of Exopolysaccharide Produced by Cyanobacterium Nostoc flagelliforme

The emulsifying, flocculating, and physicochemical properties of purified exopolysaccharide (EPS) of terrestrial cyanobacterium Nostoc flagelliforme cultured in liquid media were investigated. The EPS was defined as heteropolysaccharide composed by 41.2 % glucose, 21.1 % galactose, 21.0 % mannose, 2.5 % fructose, 3.6 % ribose, 1.7 % xylose, 0.6 % arabinose, 3.0 % rhamnose, 0.9 % fucose, and 4.3 % glucuronic acid. The EPS possessed higher intrinsic viscosity than other cyanobacterial strains as reported and displayed pseudoplastic behavior in aqueous solution. The EPS produced more stable emulsions with tested hydrocarbons and oils than xanthan gum, and the emulsification indexes with n-hexadecane, liquid paraffin, and peanut oil were higher than 50 %, indicating the strong emulsion-stabilizing capacity. The EPS showed peak flocculating rates of 93.5 and 86.1 % in kaolin and MgO suspension, respectively, and exhibited a better flocculation performance than Al₂(SO₄)₃ and xanthan gum. These results demonstrated that the EPS of N. flagelliforme was a very promising candidate for numerous industrial applications, as it had higher intrinsic viscosity, good emulsification activity, and excellent flocculation capability.     

Efficient Production of Ethanol from Empty Palm Fruit Bunch Fibers by Fed-Batch Simultaneous Saccharification and Fermentation Using Saccharomyces cerevisiae

The concentration of ethanol produced from lignocellulosic biomass should be at least 40 g l^?1 [about 5 % (v/v)] to minimize the cost of distillation process. In this study, the conditions for the simultaneous saccharification and fermentation (SSF) at fed-batch mode for the production of ethanol from alkali-pretreated empty palm fruit bunch fibers (EFB) were investigated. Optimal conditions for the production of ethanol were identified as temperature, 30 °C; enzyme loading, 15 filter paper unit g^?1 biomass; and yeast (Saccharomyces cerevisiae) loading, 5 g l^?1 of dry cell weight. Under these conditions, an economical ethanol concentration was achieved within 17 h, which further increased up to 62.5 g l^?1 after 95 h with 70.6 % of the theoretical yield. To our knowledge, this is the first report to evaluate the economic ethanol production from alkali-pretreated EFB in fed-batch SSF using S. cerevisiae.