Optimization of lactic acid production from whey by L casei NRRL B‐441 immobilized in chitosan stabilized Ca‐alginate beads

The production of lactic acid from whey by Lactobacillus casei NRRL B‐441 immobilized in chitosan‐stabilized Ca‐alginate beads was investigated. Higher lactic acid production and lower cell leakage were observed with alginate–chitosan beads compared with Ca‐alginate beads. The highest lactic acid concentration (131.2 g dm^?3) was obtained with cells entrapped in 1.3–1.7 mm alginate–chitosan beads prepared from 2% (w/v) Na‐alginate. The gel beads produced lactic acid for five consecutive batch fermentations without marked activity loss and deformation. Response surface methodology was used to investigate the effects of three fermentation parameters (initial sugar, yeast extract and calcium carbonate concentrations) on the concentration of lactic acid. Results of the statistical analysis showed that the fit of the model was good in all cases. Initial sugar, yeast extract and calcium carbonate concentrations had a strong linear effect on lactic acid production. The maximum lactic acid concentration of 136.3 g dm^?3 was obtained at the optimum concentrations of process variables (initial sugar 147.35 g dm^?3, yeast extract 28.81 g dm^?3, CaCO₃ 97.55 g dm^?3). These values were obtained by fitting of the experimental data to the model equation. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in lactic acid production using alginate–chitosan‐immobilized cells. Copyright © 2005 Society of Chemical Industry     

Biomass production by a thermotolerant yeast: Hansenula polymorpha

Biomass production at high temperature by Hansenula polymorpha as part of a lignocellulosic utilizing process was studied. Compromise growth conditions (45°C and pH = 4.8) with an eventual saccharification step were established. The effects of stirring rate and initial glucose concentration on biomass yield coefficient, volumetric productivity and maximal cell density were determined. Process optimization led to a fed-batch fermentation process: high yield (0.63 g dry cell g^?1 glucose), volumetric productivity (1.3 g dry cell dm^?3 h^?1) and cell concentration (60 g dry cell dm^?3) were obtained. At these conditions, significant arabitol excretion (18 g dm^?3) as a unique by-product associated with cell mass production was obtained, making more interesting a high temperature operating process.     

Effect of Carrier Matrix on Fermentative Production of Ethanol by Surface Immobilised Yeast Cells

The production of ethanol for potable preparations is well established and the traditional methods used therein are changing. More important, however, has been the advent of fuel alcohol, first in Brazil, but now with ever-increasing possibilities of being adopted in North America and Europe. Production of alcohol by fermentation has therefore come to stay, and it is essential to discover ways of improving the productivities of such fermentations. The effect of organic (cellulose and corn stover) and inorganic matrices (silica gel, porous silica, Celite and derivatised Celite) on the performance of ethanol fermentation by Saccharomyces bayanus was tested. The hydrophilicity degree of the support seems to play an important role in the ability of reaching high ethanol concentrations in the fermentation of 300 g dm^?3 of glucose. Cells immobilised on carriers with low hydrophilicity degree, namely Celite, lead to better results (residual glucose: 56 g dm^?3; ethanol: 111 g dm^?3) than their free counterparts (residual glucose: 136 g dm^?3; ethanol: 71 g dm^?3). Celite was selected for further cell immobilisation studies, including time of adsorption, whole cell concentration, initial glucose concentration and time of addition of the support to the fermentation medium. The latter has revealed to be a very important factor, improving the performance of ethanol fermentation by reducing the fermentation time. Previous immobilisation seems to have no effect when compared with the simple addition of Celite to the inoculated medium and the eficiency of Celite did not increase when the concentration of glucose was enhanced.     

The production of propionic acid from sugars by fermentation through lactic acid as an intermediate

As an alternative to propionic acid production from sugars by species of propionibacteria, propionic acid may be produced from sugars through lactate as an intermediate. Propionibacteria are actually able to utilize lactate as a substrate much more rapidly than glucose. In this study, Lactobacillus xylosus and Propionibacterium shermanii were utilized to convert glucose and xylose to propionate through lactate as an intermediate. Pure culture batch studies were carried out to obtain fermentation parameters for the two cultures. The pure cultures were then combined in a mixed culture series arrangement designed to prevent nutrient limitation. Finally, propionic acid production from lactate was demonstrated in a cross-linked immobilized cell reactor using lactate added to the medium and produced by L. xylosus in a continuous stirred tank reactor. Productivities of 14 g dm^?3 h^?1 at a 9 min residence time (2·1 g dm^?3 propionate) and 2 g dm^?3 h^?1 at a 9·9 h residence time (19·7 g dm^?3 propionate) were obtained without pH control.     

Continuous ethanol fermentation using immobilized yeast in a fluidized bed reactor

Continuous ethanol fermentation of glucose using fluidized bed technology was studied. Saccharomyces cerevisiae were immobilized and retained on porous microcarriers. Over two-thirds of the total reactor yeast cell mass was immobilized. Ethanol productivity was examined as dilution rate was varied, keeping all other experimental parameters constant. Ethanol yield remained high at an average of 0.36 g ethanol g^?1 glucose (71% of theoretical yield) as the dilution rate was increased stepwise from 0.04 h^?1 to 0.14 h^?1. At a dilution rate of 0.15 h^?1, the ethanol yield steeply declined to 0.22 g ethanol g^?1 glucose (44% of theoretical yield). The low maximum percentage of theoretical yield is primarily due to an extended mean cell residence time, and possibly due to the inhibitory effect of a high dissolved carbon dioxide concentration, enhanced by the probable intermittent levels of low pH in the reactor. Constant ethanol production was possible at a high glucose loading rate of 840 g dm^?3 day^?1 (attained at a dilution rate of 0.14 h^?1). Although the highest average ethanol concentration (97.14 g dm^?3) occurred at the initial dilution rate of 0.04 h^?1, the peak average ethanol production rate (2.87 g (g yeast)^?1 day^?1) was reached at a greater dilution rate of 0.11 ^h-1. Thus, the optimal dilution rate was determined to be between 0.11 h^?1 and 0.14 h^?1. Ethanol inhibition on yeast cells was absent in the reactor at average bulk-liquid ethanol concentrations as high as 97.14 g dm^?3. In addition, zero-order kinetics on ethanol production and glucose utilization was evident.     

Production of fructooligosaccharides by β‐fructofuranosidase from Aspergillus sp 27H

β‐fructofuranosidase (EC 3.2.1.26) from Aspergillus sp 27H isolated from soil was investigated for production of fructooligosaccharides (FOS) using whole cells. It possesses hydrolytic and transfructosylating activities that can be altered by modifying the reaction conditions. The optimal conditions for the transfructosylating activity occur in the pH range 5.5–6.0 and at 60 °C, while hydrolytic activity was highest at pH 4.0 and 55 °C. At low sucrose concentration (10 g dm^?3) there was rapid conversion of sucrose to glucose and fructose and very low concentrations of FOS were obtained. However, at sucrose concentrations higher than 216 g dm^?3 the concentrations of hydrolysis products were reduced. Under the following conditions: pH 5.5, temperature 40 °C, sucrose concentration 615 g dm^?3 and enzyme concentration 20β‐fructofuranosidase units g^?1 of sucrose, the FOS concentration reached a maximum value of 376 g dm^?3 (234 g dm^?3 1‐kestose and 142 g dm^?3 nystose) and the proportion of FOS in the solids in the reaction mixture was 600–620 g kg^?1 at 6 h. These results suggest that β‐fructofuranosidase from Aspergillus sp 27H could be an appropriate enzyme for the commercial production of FOS. Copyright © 2004 Society of Chemical Industry     

Effects of polyacrylamide‐co‐acrylic acid on cellulose production by Acetobacter xylinum

Polyacrylamide‐co‐acrylic acid (PA) added to shake flask cultures of Acetobacter xylinum at concentrations up to 3 g dm^?3 resulted in increased production of bacterial cellulose. For PA concentrations of 0–3 g dm^?3, 7‐day cellulose production rose monotonically from 2.7 ± 0.8 to 6.5 ± 0.5 g dm^?3 at a shaker speed of 175 rpm, and from 1.7 ± 0.01 to 3.7 ± 0.5 g dm^?3 at shaker speed of 375 rpm. Addition of PA also changed the morphology of the biomass from amorphous/stringy forms to spheroidal particles with diameters ≤2 mm. Similarly, bioreactor cultures grown in the absence of PA formed long fibrous masses which deposited on the internals, while those grown in the presence of 1–2 g dm^?3 PA formed small discrete particles with diameters ≤0.1 mm. Tests performed with 1 and 2 g dm^?3 PA, and stirrer speeds from 500 to 900 rpm, appeared to give the highest cellulose concentration of 5.3 ± 0.7 g dm^?3 in 64–68.5 h in the presence of 2 g dm^?3 PA at 700 rpm, although this value was statistically indistinguishable from that obtained at 1 g dm^?3 PA and 900 rpm. A qualitative model is proposed to describe the mechanisms by which PA affects biomass morphology, resulting in its advantageous formation as small, dispersed, spheroidal pellets. Quantitative analysis of the results gave inverse correlations between both the fraction of fructose carbon going to cellulose synthesis and the specific fructose consumption rate, and the maximum cellulose concentration and the fraction of fructose carbon going to by‐product formation. Since cellulose yield was almost universally improved by higher polyacrylamide concentration, it appears likely that increased viscosity reduces fructose uptake rate by limiting mass transfer. Copyright © 2003 Society of Chemical Industry     

Maximizing the production of acetone—butanol in an alginate bead fluidized bed reactor using clostridium acetobutylicum

Low volumetric solvent productivities are one of the characteristics of an acetone-butanol fermentation by C. acetobutylicum. A calcium alginate immobilized continuous culture was used in a novel gas-sparged reactor to strip the solvents from the aqueous phase and reduce their toxicity. A dilution rate of 0.07 h^?1 was found to give maximum solvent productivity at 0.58 g dm^?3 h^?1, although at 0.12 h^?1 the productivity was slightly lower. In order to increase glucose uptake by the culture, feed glucose concentrations were increased over time to attempt to acclimatize the culture. This resulted in a productivity as high as 0.72 g dm^?3 h^?1 although this production rate was found to be unstable.     

Batch production of L(+) lactic acid from whey by Lactobacillus casei (NRRL B‐441)

The effects of temperature, pH, and medium composition on lactic acid production by Lactobacillus casei were investigated. The highest lactic acid productivity values were obtained at 37 °C and pH 5.5. The productivity was 1.87 g dm^?3 h^?1 at 37 °C in shake flasks. In the fermenter, a productivity of 3.97 g dm^?3 h^?1 was obtained at pH 5.5. The most appropriate yeast extract concentration was 5.0 g dm^?3. Whey yielded a higher productivity value than the analytical lactose and glucose. Initial whey lactose concentration did not affect lactic acid productivity. MnSO₄ ·H₂O was necessary for lactic acid production by L casei from whey. Product yields were approximately 0.93 g lactic acid g lactose^?1. Copyright © 2004 Society of Chemical Industry     

Particle Adhesion in Model Systems: 16. Barium Sulfate Particles on Glass and Protein Surfaces

The adhesion phenomena of monodispersed barium sulfate (BaSO₄) particles on gelatin-coated glass beads were evaluated using the packed column technique and compared with the same system in the absence of the protein.

Multilayer deposition was observed with the uncoated glass beads at pH 4, 5 and 6, while at pH 9, which is above the isoelectric point (pH ～ 6) of BaSO₄ particles, monolayer deposition took place, even though the BaSO₄ particles and glass beads bore the same sign of charge. At pH = 10, no uptake was observed on the glass beads, but the addition of 10^?4 mol dm^?3 BaCl₂ induced multilayer deposition due to the adsorption of the Ba²⁺ cation on BaSO₄ particles, which causes a reversal of their charge to positive.

The formation of multilayers was found to occur over a much wider pH range on the gelatin coated glass beads.

BaSO₄ particles deposited in multilayers could not be removed from either glass beads or gelatin-coated glass beads by rinsing the loaded column with solutions of pH 11.5, but could be detached from monolayers on glass beads only.     

Electrochemical production of cuprous oxide and metallic nickel in a two-compartment cell

The purpose of the present investigation was to develop an electrochemical process to obtain simultaneously cuprous oxide powder and metallic nickel in a two-compartment cell. Nafion® 901 bimembrane (Dupont, USA) was employed to separate the compartments to avoid the diffusion of nickel ions from the catholyte to the anolyte. A continuous addition of sodium hydroxide solution to the anodic compartment was necessary to form in situ the cuprous oxide by chemical reaction with the cuprous chlorocomplexes generated at the anode. As an anode system, a titanium basket filled with copper scrap wire was utilized. The anodic operating conditions were: NaCl 250 g dm^?3, pH 10, 80°C, c.d. 6 A dm^?2 and current concentration 0.4 A dm^?3, The cathodic parameters were: Ni²ⁱ 74 g dm^?3, H₃B0₃30 g dm^?3, sodium lauryl sulphate 0.5 g dm^?3, coumarin 0.15 g dm^?3, pH2, 50°C, c.d. 6 A dm^?2 Good quality red-violet cuprous oxide powder, meeting ASTM specifications D912-65 to be used in antifouling paints and metallic nickel (> 99.96% Ni) was obtained.     

Solvent Impregnated Resins containing Quinizarin: Preparation and Application to Batch‐mode Separation of Cd(II), Cu(II), Ni(II), and Zn(II) in Aqueous Media Prior to the Determination by Flame Atomic Absorption Spectrometry

Abstract

Preparation of a high stable solvent impregnated resins (SIR) containing 1,4‐dihydroxyanthraquinone (quinizarin, QNZ) was proposed using Amberlite XAD‐16 beads. The SIR was applied for the separation of Cd(II), Cu(II), Ni(II), and Zn(II) in aqueous media prior to the determination by flame atomic absorption spectrometry (FAAS). The optimum conditions for batch mode extraction of the above metal ions were investigated and it was found that the sorption of these metal ions from a 1000‐ml aliquots of the solution on 1.5 g of the SIR can be carried out quantitatively at pH of 9.5 and an ionic strength of 0.01 mol dm^?3. The sorbed metal ions were subsequently eluted with 10 ml 2 mol dm^?3 HCl and the eluent was subjected to FAAS. Beer's law was obeyed in the range of 9×10^?9 ?1×10^?7 mol dm^?3 for Cd(II) and Zn(II), and 9×10^?8 ?1×10^?6 mol dm^?3 for Cu(II) and Ni(II) contents. Significant interference was not observed due to the various ions, which could be found in natural water samples. The practical applicability of the method was confirmed using a synthetic certificated reference material (CRM) and spiked natural water samples.     

Effect of an electric field on the transport of Th(IV) in the presence of Eu(III) and U(VI) through supported liquid membrane containing di‐2‐ethylhexylphosphoric acid

This paper investigates the transport of Th(IV) ions in nitric acid media through a supported liquid membrane (SLM) impregnated with di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene using an electric field. The transport was carried out in a three compartment cell fitted with microporous cellulose nitrate (SLM) and cation exchange membrane (Nafion). The effect of different parameters including nitric acid concentration in the feed solution, HDEHP concentration in the membrane, and HCl concentration were studied. The optimal conditions for Th(IV) transport were 0.1 mol dm^?3 HDEHP, 10^?3 mol dm^?3 HNO₃ in the feed solution, 1 mol dm^?3 HCl in compartment 2 and 1 mol dm^?3 HCl in compartment 3 at 25 °C. Under the optimal conditions of Th(IV) transport the recovery factor after 90 min was 0.25 without applying an electrostatic field, compared with 0.9 when the electric field was applied. The effect of electric current on the flux of Th(IV) through the membrane was also studied. The flux increased as the current density increased from 10 to 30 mA cm^?2 to reach a maximum value at 30 mA cm^?2 (8 × 10^?9 g eq cm^?2 s^?1). The transport percentages of 0.3 g dm^?3 Th(IV) in the presence of 0.1 g dm^?3 Eu(III) and 1 g dm^?3 U(VI) were 66, 84 and 15%, respectively. The determined selectivities of U(VI)–Th(IV) and Th(IV)–Eu(III) were 0.12 and 0.3, respectively, after 90 min. Therefore, the order of selectivity of this system is Eu(III) > Th(IV) > U(VI). © 2001 Society of Chemical Industry     

Production of lactic acid from beet molasses by calcium alginate immobilized Lactobacillus delbrueckii IFO 3202

Lactic acid was produced from pretreated beet molasses by the homofermentative organism Lactobacillus delbrueckii subsp delbrueckii IFO 3202 entrapped in calcium alginate gel using batch, repeated batch and continuous fermentation systems. In batch fermentation studies successful results were obtained with 2.0–2.4 mm diameter beads prepared from 2% sodium alginate solution. The highest effective yield (82.0%) and conversion yield (90.0%) were obtained from substrate concentrations of 52.1 and 78.2 g dm⁻³ respectively. The gel beads produced lactic acid for 14 consecutive batch fermentations without marked activity loss and deformation. In the continuous fermentation, the highest lactic acid (4.22%) was obtained at a dilution rate of 0.1 h⁻¹ while the highest productivity (13.92 g dm⁻³ h⁻¹) was obtained at a dilution rate of 0.4 h⁻¹. © 1999 Society of Chemical Industry     

Utilization of response surface methodology to optimize the culture media for the production of rhamnolipids by Pseudomonas aeruginosa AT10

Pseudomonas aeruginosa AT10 produced a mixture of surface‐active rhamnolipids when cultivated on mineral medium with waste free fatty acids as carbon source. The development of the production process to an industrial scale included the design of the culture medium. A 2⁴ full factorial, central composite rotational design and response surface modelling method (RSM) was used to enhance rhamnolipid production by Pseudomonas aeruginosa AT10. The components that are critical for the process medium were the carbon source, the nitrogen source (NaNO₃), the phosphate content (K₂ HPO₄/KH₂PO₄ 2:1) and the iron content (FeSO₄·7H₂O). Two responses were measured, biomass and rhamnolipid production. The maximum biomass obtained was 12.06 g dm^?3 DCW, when the medium contained 50 g dm^?3 carbon source, 9 g dm^?3 NaNO₃, 7 g dm^?3 phosphate and 13.7 mg dm^?3 FeSO₄·7H₂O. The maximum concentration of rhamnolipid, 18.7 g dm^?3, was attained in medium that contained 50 g dm^?3 carbon source, 4.6 g dm^?3 NaNO₃, 1 g dm^?3 phosphate and 7.4 mg dm^?3 FeSO₄·7H₂O. © 2002 Society of Chemical Industry     

Optimization of pullulan production using Ca‐alginate‐immobilized Aureobasidium pullulans by response surface methodology

BACKGROUND: The production of pullulan from synthetic medium by Aureobasidium pullulans P56 immobilized in Ca‐alginate beads was investigated using batch and repeated batch fermentation systems. RESULTS: The highest pullulan concentration (19.52 ± 0.37 g dm^?3) was obtained with 2.0‐2.4 mm beads prepared from 2% sodium alginate solution. Pullulan production was mainly accomplished by immobilized fungal cells since leaked cells in the fermentation medium comprised 17.4% of the total fungal population at the end of fermentation. The pullulan proportion was 84.5% of the total polysaccharide in the fermentation medium. Response surface methodology was used to investigate the effects of three fermentation parameters (initial pH, agitation speed and incubation time) on the concentration of pullulan. Results of the statistical analysis showed that the fit of the model was good in all cases. The maximum pullulan concentration of 21.07 ± 0.48 g dm^?3 was obtained at the optimum concentrations of process variables (pH 7.31, agitation speed 191.5 rpm, incubation time 101.2 h). The gel beads produced pullulan under the optimized conditions for six consecutive batch fermentations without marked activity loss and deformation. CONCLUSION: The results of this study suggest that the immobilization of A. pullulans cells in Ca‐alginate gel beads is suitable for batch and repeated batch production of pullulan. Copyright © 2007 Society of Chemical Industry     

The dynamics of aerobic phenol biodegradation in lower greensand

The dynamics of phenol degradation in sedimentary rocks was examined by percolating phenol solutions, with no added nutrients, through columns of disturbed Lower Greensand. Phenol degradation was achieved at concentrations up to 16.7 g dm^?3. Inhibition was evident at higher concentrations. Sterilisation of Lower Greensand by moist heat or irradiation completely destroyed its ability to degrade phenol. Non-growing bacterial cells attached to sand and clay particles were responsible for phenol degradation. Zero- and first-order rate values for phenol degradation increased with increasing flowrate. First-order kinetics operated with respect to substrate concentration. At flowrates of 1 cm³ h^?1 (0.063 cm h^?1) the reaction approached zero-order at phenol concentration above 9.2 g dm^?3 but at flowrates of 3 cm³ h^?1 (0.19 cm h^?1) increasing the phenol input concentration above 9.7 g dm^?3 resulted in strong inhibition of activity. The results are explained in terms of phenol degradation being limited by the diffusion of phenol across a stagnant liquid film surrounding the microbes.     

Simultaneous removal of atrazine and nitrate using a biological granulated activated carbon (BGAC) reactor

The objective of this research was to characterize the performance of granulated activated carbon (GAC) as a carrier for Pseudomonas ADP in a non‐sterile continuous fluidized bed reactor for atrazine degradation under anoxic conditions. The GAC was compared with two non‐adsorbing carriers: non‐adsorbing carbon particles (‘Baker product’) having the same surface area available for biofilm growth as the GAC, and sintered glass beads. The initial atrazine degradation efficiency was higher than 90% in the reactors with the non‐adsorbing carriers, but deteriorated to 20% with time due to contamination by foreign denitrifying bacteria. In contrast, no deterioration was observed in the biological granulated activated carbon (BGAC) reactor. A maximal atrazine volumetric and specific degradation rate of 0.820 ± 0.052 g atrazine dm^?3 day^?1 and 1.7 ± 0.4 g atrazine g^?1 protein day^?1 respectively were observed in the BGAC reactor. Concurrent atrazine biodegradation and desorption from the carrier was shown and an effluent concentration of 0.002 mg dm^?3 (below the EPA standard) was achieved in the BGAC reactor. The advantages of the BGAC reactor over the non‐adsorbing carrier reactors can probably be explained by the adsorption–desorption mechanism providing favorable microenvironmental conditions for atrazine–degrading bacteria. Copyright © 2004 Society of Chemical Industry     

Production of protease by bacillus subtilis using simultaneous control of glucose and ammonium concentrations

Batch, ammonium-controlled and simultaneous glucose and ammonium controlled fermentations were compared for the production of protease by Bacillus subtilis NCIB 8054. During fermentations of B. subtilis, maximum protease production was obtained in the stationary phase. Protease production in fermentations controlled at 5 mmol dm^?3 ammonium was 1.5 times greater than in uncontrolled batch fermentations. Simultaneous control of ammonium at 5 mmol dm^?3 and glucose at 0.15 g dm^?3 using controllers based on an ammonium electrode and an oxygen electrode, doubled protease production compared with fermentations having only an ammonium control and tripled protease production compared with uncontrolled batch fermentations. The protease yield on glucose and protease yield on ammonium was increased in fermentations with simultaneous glucose and ammonium control.     

Optimization of the glucose feed rate profile for the production of tryptophan from recombinant E coli

A strain of Escherichia coli was engineered to overproduce L ‐tryptophan. A fed‐batch fermentation process was developed, producing 30.8 ± 1.4 g dm^?3 with a yield on glucose of 0.132 ± 0.010 g g^?1. Specific production rate did not appear to be limited by cloned enzyme activity, but by the carbon flux from central metabolism into the aromatic amino acid pathway. The glucose feed rate profile was modified in an attempt to increase the production rate. Tryptophan production was not affected, but led to glutamic acid excretion at high levels. The high specific glucose consumption rate at the low growth rate led to the high glutamate excretion. A new fermentation process involving modification of the feed profile to limit the formation of by‐products was discovered. The resulting final process increased tryptophan production to 42.3 ± 2.7 g dm^?3 with yield on glucose of 0.176 ± 0.006 g g^?1. The instantaneous yield realized the theoretical maximum for the majority of the fermentation. © 2002 Society of Chemical Industry