Showing papers in "Applied Biochemistry and Biotechnology in 1992"
TL;DR: In this article, the simultaneous saccharification and fermentation (SSF) based wood-to-ethanol process was investigated and the combined effects of optimizing SSF enzyme loading, increasing plant capacity to 10,000 dry t/d, and reducing wood cost to $34/dry t are to reduce the preliminary estimate of the production cost to about $0.95/gal.
Abstract: The Solar Energy Research Institute (SERI) recently completed a detailed engineering and economic analysis of the simultaneous saccharification and fermentation (SSF) based wood-to-ethanol process. The reference-case design was based on a plant capacity of 1920 dry t/d and a wood cost of $42/dry t. For this case, the preliminary estimate of the production cost of the ethanol product is about $1.22/gal. The combined effects of optimizing SSF enzyme loading, increasing plant capacity to 10,000 dry t/d, and reducing wood cost to $34/dry t are to reduce the preliminary estimate of the production cost to about $0.95/gal. Other technological improvements may further reduce the production cost. Certain technical assumptions, inherent in the analysis, are being investigated further.
183 citations
TL;DR: In this paper, the same number of milliequivalents of base/weight of wood remove the same extent of acetyl groups, regardless of the concentration of the base solution, and no cation effects are found among Li, Na, and K alkali hydroxide solutions.
Abstract: Aspen wood substrates with varying degrees of deacetylation, xylan, and lignin removal have been prepared and submitted to enzymatic hydrolysis with a cellulase/hemicellulase preparation for an extended constant period of hydrolysis. Controlled deacetylation has been achieved by treating wood with various alkali metal hydroxide solutions, at various alkali/wood ratios. It has been found that samples with the same extent of deacetylation produce the same sugar yields upon enzymatic hydrolysis. Increased degree of deacetylation increases the yield of sugars obtained from enzymatic hydrolysis, all other compositional parameters held constant. The acetyl group removal is proportional to the stoichiometric relation between added base and wood acetyl content, i.e., the same number of milliequivalents of base/weight of wood remove the same extent of acetyl groups, regardless of the concentration of the base solution. No cation effects are found among Li, Na, and K alkali hydroxide solutions, suggesting that swelling is not as important a parameter as is the removal of the acetyl groups from the xylan backbone in determining the extent of hydrolyzability of the resulting sample.
180 citations
TL;DR: In this paper, enzymatic hydrolysis of SO2-impregnated, steam-exploded Eucalyptus viminalis was carried out at increasing substrate concentrations and enzyme loadings.
Abstract: Enzymatic hydrolysis of SO2-impregnated, steam-explodedEucalyptus viminalis was carried out at increasing substrate concentrations and enzyme loadings. When low enzyme loadings were used, the peroxide-treated fraction derived from eucalyptus chips (SEE-WIA/ H2O2) was more readily hydrolyzed than the water-insoluble (SEE-WI) and the alkali-insoluble (SEE-WIA) fractions. The various cellulosic fractions derived from steam-explodedE. viminalis exhibited a greater susceptibility to hydrolysis than the equivalent aspen and spruce substrates, particularly at high substrate concentrations (10%, w/v).
169 citations
TL;DR: In this paper, the Ammonia Fiber Explosion (AFEX) process was applied to mixed municipal solid waste (MSW) and individual components (e.g., softwood newspaper, kenaf newspaper, copy paper, paper towels, cereal boxes, paper bags, corrugated boxes, magazines, and waxed paper).
Abstract: The Ammonia Fiber Explosion (AFEX) process treats lignocellulose with high-pressure liquid ammonia and then explosively releases the pressure. The combined chemical effect (cellulose decrystallization) and physical effect (increased accessible surface area) dramatically increase lignocellulose susceptibility to enzymatic attack. For example, bagasse digestibility is increased 5.5 times and that of kenaf core is increased 11 times using extracellular cellulases fromTrichoderma reesei. In this study, we applied the AFEX process to mixed municipal solid waste (MSW) and individual components (e.g., softwood newspaper, kenaf newspaper, copy paper, paper towels, cereal boxes, paper bags, corrugated boxes, magazines, and waxed paper). Softwood newspaper proved to be the most difficult component to digest because of its high lignin content. A combination of oxidative lignin cleavage and AFEX was required to increase softwood newspaper digestibility substantially, whereas AFEX alone was able to make kenaf newspaper digestible. Because most MSW components have been substantially delignified in the paper-making process, AFEX only marginally increased their digestibility.
159 citations
TL;DR: The results of the simultaneous saccharification and fermentation (SSF) experiments indicate that the cellulose in pretreated wheat straw can be efficiently fermented into ethanol for up to a 15% cellulose concentration (244% straw concentration) as mentioned in this paper.
Abstract: Wheat straw was pretreated with dilute (05%) sulfuric acid at 140°C for 1 h Pretreated straw solids were washed with deionized water to neutrality and then stored frozen at –20°C The approximate composition of the pretreated straw solids was 64% cellulose, 33% lignin, and 2% xylan The cellulose in the pretreated wheat straw solids was converted to ethanol in batch simultaneous saccharification and fermentation experiments at 37°C using cellulase enzyme fromTrichoderma reesei (Genencor 150 L) with or without supplementation with β–glucosidase fromAspergillus niger (Novozyme 188) to produce glucose sugar and the yeastSaccharomyces cerevisiae to ferment the glucose into ethanol The initial cellulose concentrations were adjusted to 75, 10, 125, 15, 175, and 20% (w/w) Since wheat straw particles do not form slurries at these concentrations and cannot be mixed with conventional impeller mixers used in laboratory fermenters, a simple rotary fermenter was designed and fabricated for these experiments The results of the simultaneous saccharification and fermentation (SSF) experiments indicate that the cellulose in pretreated wheat straw can be efficiently fermented into ethanol for up to a 15% cellulose concentration (244% straw concentration)
158 citations
TL;DR: The darkly colored polyphenols induce the problem of biodegradation of OMW, whereas the long chain fatty acids (LCFA), tannins and simple phenolic compounds are responsible its toxicity for methanogenic bacteria.
Abstract: The anaerobic biodegradability and toxicity of olive mill waste-waters (OMW) were studied in batch anaerobic digestion experiments. Anaerobic digestion of OMW or the supernatant of its centrifugation, the methane production was achieved at up to 5–15% (V/V) dilution corresponding to only 5–20 g/L COD. The washed suspended solids of OMW were toxic at up to 80 g/L COD; however, the kinetic of biodegradability of OMW or the supernatant was faster than for suspended solids, which are constituted meanly of cellulose and lignin. The darkly colored polyphenols induce the problem of biodegradation of OMW, whereas the long chain fatty acids (LCFA), tannins and simple phenolic compounds are responsible its toxicity for methanogenic bacteria.
132 citations
TL;DR: Two additional electrophoretically distinct molecular forms, isoforms (iso) 2 and 3, with lectin properties were isolated from Ratylia mollis Mart, seeds (FABACEAE), and showed distinct specificity.
Abstract: Two additional electrophoretically distinct molecular forms, isoforms (iso) 2 and 3, with lectin properties were isolated fromCratylia mollis Mart, seeds (FABACEAE), by extraction with 0.15M NaCl and ammonium sulfate fractionation, followed by chromatography on Sephadex G-75 and Bio-Gel P-200 (iso 2), as well as CM-Cellulose and Sephadex G-75 (iso 3). Both isoforms were human group nonspecific and showed distinct specificity. Polyacrylamide gel electrophoresis resolved iso 2 and 3 in polypeptides of apparent mol wts 60 and 31 kDa, respectively; a distinct isoelectric focusing pattern was obtained for iso 2 and 3, under denaturing and reducing conditions.
89 citations
TL;DR: In this article, an equilibrium and rate relationship for the sorption of divalent copper (Cu2+) and hexavalent chromium (Cr6+) onto untreated Red Fir sawdust was determined.
Abstract: Equilibrium and rate relationships have been determined for the sorption of divalent copper (Cu2+) and hexavalent chromium (Cr6+) onto untreated Red Fir sawdust. For both ions, the equilibrium sorption levels were determined to be a function of the solution pH and temperature. The equilibrium adsorption capacity of the sawdust for Cu2+ was found to increase with increasing pH. However, for Cr6+ the sorption capacity increased with decreasing pH. For both ions, the rate of adsorption and the equilibrium adsorption capacity increased with temperature. The sorption capacity of α-cellulose was at least an order of magnitude less than the untreated sawdust.
83 citations
TL;DR: Results demonstrate the potential of LDOF photobioreactor units for CO2 removal and biomass production using marine cyanobacteria.
Abstract: A light diffusing optical fiber (LDOF) photobioreactor with an improved gas input system has been used for the high-density culture of a marine cyanobacterium Synechococcus sp. Optimum conditions for CO2 removal and biomass production were investigated. Maximum CO2 removal of 4.44 g/L/d was achieved using an initial cell concentration of 6.8 g/L. The biomass yield was 0.97 g/L for a 12-culture time. Continuous cultures, in which medium was filtered using a ceramic membrane module, showed enhanced growth, with a final cell concentration of 11.2 g/L. These results demonstrate the potential of LDOF photobioreactor units for CO2 removal and biomass production using marine cyanobacteria.
72 citations
TL;DR: An analysis of the maximum theoretical yield of 1,3-PD from glycerol indicates that the yield can be improved by the cofermentation of sugars, provided that kinetic constraints are overcome.
Abstract: 1,3-Propanediol (1,3-PD) is an intermediate in chemical and polymer synthesis. We have previously expressed the genes of a biochemical pathway responsible for 1,3-PD production, the dha regulon of Klebsiella pneumoniae, in Escherichia coli. An analysis of the maximum theoretical yield of 1,3-PD from glycerol indicates that the yield can be improved by the cofermentation of sugars, provided that kinetic constraints are overcome. The yield of 1,3-PD from glycerol was improved from 0.46 mol/mol with glycerol alone to 0.63 mol/mol with glucose cofermentation and 0.55 mol/mol with xylose cofermentation. The engineered E. coli also provides a model system for the study of metabolic pathway engineering.
69 citations
TL;DR: It has been observed that the coupled system was advantageous over the two stage (separate hydrolysis/fermentation) system as it produced higher amounts of ethanol from cellulose (3.6% as compared to 2.3% ethanol from rice straw).
Abstract: Using cellulase/hemicellulase complex of Sclerotium rolfsii UV-8 mutant and Saccharomyces cerevisiae for fermentation, the coupled saccharification/fermentation (CSF) of 15% AT-rice straw was carried out at 40 degrees C, pH 4.5 for the first 24 h and further incubation was performed at 30 degrees C for 72 h. Increasing the amount of cellulase activity from 3-12 IU FPA/g of substrate resulted in increased yields of ethanol from 1.5-3.6% in 96 h. It has been observed that the coupled system was advantageous over the two stage (separate hydrolysis/fermentation) system as it produced higher amounts of ethanol from cellulose (3.6% as compared to 2.3% ethanol from rice straw).
TL;DR: A mathematical model that depicts the kinetics of SSF has been developed based on considerations of the quality of the substrate and enzyme, and the substrate-enzyme-microorganism interactions and will be used for rational SSF optimization and scale-up.
Abstract: Ethanol, a promising alternative fuel, can be produced by the simultaneous saccharification and fermentation (SSF) of lignocellulosic biomass, which combines the enzymatic hydrolysis of cellulose to glucose and the fermentation of glucose to ethanol by yeast in a single step. A mathematical model that depicts the kinetics of SSF has been developed based on considerations of the quality of the substrate and enzyme, and the substrate-enzyme-microorganism interactions. Critical experimentation has been performed in conjunction with multiresponse nonlinear regression analysis to determine key model parameters regarding cell growth and ethanol production. The model will be used for rational SSF optimization and scale-up.
TL;DR: The optical absorption spectra of the polyaniline/glucose oxidase electrode after glucose had been added to the buffer solution showed that the absorption band around 800 nm had changed considerably when glucose was allowed to react with the electrode, which makes polyAniline a very promising polymer for use as a support in optical sensor for clinical application.
Abstract: A biosensor for glucose utilizing kinetics of glucose oxidase (EC 1.1.3.4.) was developed. The enzyme was immobilized on polyaniline by covalent bonding, using glutaraldehyde as a bifunctional agent. The system showed a linear response up to 2.2 mM of glucose with a response time of 2.5-4.0 min. In addition, the immobilized enzyme had a higher activity between pH 6.5 and 7.5. The system retained 50% of its activity after 30 d of daily use. The optical absorption spectra of the polyaniline/glucose oxidase electrode after glucose had been added to the buffer solution showed that the absorption band around 800 nm had changed considerably when glucose was allowed to react with the electrode. This optical variation makes polyaniline a very promising polymer for use as a support in optical sensor for clinical application.
TL;DR: A biocompatible needle-type glucose sensor with a 3-electrode configuration that showed a rapid response, good reproducibility, good stability, and a wide dynamic range was used to determine glucose in serum.
Abstract: A biocompatible needle-type glucose sensor with a 3-electrode configuration was constructed. A platinum-electroplated carbon stick was used as the working electrode, Ag/AgCl as the reference electrode, and a disposable hypodermic needle made of stainless steel as the counter electrode. A Nafion membrane, an immobilized glucose oxidase (GOD) membrane, and a biocompatible membrane with diffusion-limiting effect were coated successively onto the working electrode. The sensor showed a rapid response ( 0.95).
TL;DR: In this article, the authors have demonstrated that trinitrotoluene (TNT) and cyclotrimethylene trinitramine (RDX) can be effectively treated by Phanerochaete chrysosporium immobilized on the disks of a rotating biological contractor (RBC) in both batch and continuous modes.
Abstract: “Pink water” is a waste-water stream generated by munitions LAP (loading, assembly, and packing) operations. The major components of this waste water are trinitrotoluene (TNT) and cyclotrimethylene trinitramine (RDX) at concentrations of 120-175 mg/L and 25 mg/L, respectively. Currently, pink water is treated by activated carbon adsorption. Removal efficiencies of >99.5% have been reported. However, this treatment method suffers a serious limitation in that the carbon cannot be safely regenerated. Loaded carbon is disposed of by incineration after a single use. We have demonstrated that TNT, RDX, simulated, and actual pink water can be effectively treated byPhanerochaete chrysosporium immobilized on the disks of a rotating biological contractor (RBC) in both batch and continuous modes. Greater than 90% removal of TNT from a simulated pink water was observed in a continuous RBC with a residence time of about 24 h. The disk area required was about 10,000 ft2/gpm (4091 m2/m3h) feed. RDX was amenable to treatment, but RDX removal rates were somewhat slower. A full-scale treatment system was designed on the basis of laboratory data, and a cost analysis was performed. This analysis has shown that biotreatment of pink water can be a cost-effective alternative to carbon adsorption.
TL;DR: In this article, a cDNA expression library was constructed for cyclotella cryptica and a genomic library for several other algal species, and the libraries were screened with heterologous or homologous probes for nitrate reductase and acetyl-CoA carboxylase in order to clone these genes.
Abstract: Significant progress has been made toward the successful genetic engineering of microalgal species with high potential for fuel production. Foreign DNA has been transferred into a green alga,Chlorella ellipsoidea, and has been successfully expressed in this heterologous system. In addition, electroporation has shown promise as a means of introducing DNA into intact algal cells. We have analyzed the composition of DNA from several algal species and demonstrated the presence of elevated GC contents in several green algal species. These results suggest that homologous selectable markers may be required for the development of stable transformation systems for the algae; the development of nitrate reductase and orotidine-5′-phosphate decarboxylase as homologous selectable markers forMonoraphidium minutum and forCyclotella cryptica is in progress. We have constructed a cDNA expression library forCyclotella cryptica, and are constructing cDNA and genomic libraries for several other algal species. The libraries will be screened with heterologous or homologous probes for nitrate reductase and acetyl-CoA carboxylase in order to clone these genes, which appear to influence lipid accumulation in the algae. This work represents important steps toward the genetic improvement of micro-algae for fuel production.
TL;DR: The performance of Rhodospirillum rubrum in continuous stirred-tank and trickle-bed reactors is addressed, with particular attention given to the importance of mass-transfer and reaction kinetics in modeling reactor performance.
Abstract: In designing bioreactors for the conversion of sparingly soluble gases, both mass transfer and kinetic effects must be considered.Rhodospirillum rubrum, an anaerobic photosynthetic bacterium capable of carrying out the water gas shift reaction, is an ideal organism for studying the relative importance of mass-transfer and kinetics since the cell concentration in continuous reactors employingR. rubrum may be regulated by the quantity of light supplied to the bacterium. This article addresses the performance ofR. rubrum in continuous stirred-tank and trickle-bed reactors, with particular attention given to the importance of mass-transfer and reaction kinetics in modeling reactor performance. Estimates of mass-transfer coefficients are made for a trickle-bed reactor system based upon reactor performance equations and experimental observations.
TL;DR: In this paper, a fluidized-bed reactor using immobilized cells in a continuous fermentation process, coupled with product removal and concentration by a membrane process, is a viable option.
Abstract: Traditional technology for ABE production and recovery does not allow an economic process. However, use of a fluidized-bed reactor using immobilized cells in a continuous fermentation process, coupled with product removal and concentration by a membrane process, is a viable option. The major factor affecting product price is the substrate cost. Membrane selectivity and flux have little effect.
TL;DR: The range of morphological forms of actinomycetes in shaken flask culture and fermenters is reviewed and the relationship between morphology and production of antibiotics and other metabolites is examined.
Abstract: The range of morphological forms of actinomycetes in shaken flask culture and fermenters is reviewed. Some of the factors that influence pellet formation and its prevention are discussed. The relationship between morphology and production of antibiotics and other metabolites is also examined.
TL;DR: The maximal degree of the hemoglobin-catalyzed dibenzothiophene oxidation was predicted, and found, to be strongly dependent on the reaction medium composition.
Abstract: Biocatalytic oxidation of dibenzothiophene (a model of organic sulfur in coal) with hydrogen peroxide was investigated. It was found that various hemoproteins, both enzymic (e.g., horseradish peroxidase) and nonenzymic (e.g., bovine blood hemoglobin), readily oxidized dibensothiophene to its S-oxide and, to a minor extent, further to its S-dioxide (sulfone). This process catalyzed by hemoglobin (a slaughterhouse waste protein) was studied in a number of monophasic aqueousorganic mixtures. Although hemoglobin was competent as an oxidation catalyst even in nearly dry organic solvents (with protic, acidic solvents being optimal), the highest conversions were observed in predominantly aqueous media. The hemoglobin-catalyzed oxidation of dibenzothiophene at low concentrations of the protein stopped long before all the substrate was oxidized. This phenomenon was caused by inactivation of hemoglobin by hydrogen peroxide that destroyed the heme moiety. The maximal degree of the hemoglobin-catalyzed dibenzothiophene oxidation was predicted, and found, to be strongly dependent on the reaction medium composition.
TL;DR: Two alcohol resistant strains ofSaccharomyces cerevisiae species were isolated from a Greek vineyard plantation and were found to be more alcohol tolerant and fermentative in the fermentation of molasse than the traditional baker’s yeast.
Abstract: Two alcohol resistant strains of Saccharomyces cerevisiae species were isolated from a Greek vineyard plantation. The strain AXAZ-1 gave a concentration of 17.6% v/v alcohol and AXAZ-2 16.5%, when musts from raisin and sultana grapes, respectively, were employed in alcoholic fermentations. They were found to be more alcohol tolerant and fermentative in the fermentation of molasse than the traditional baker's yeast. Specifically, using an initial [symbol: see text] Be density of 16 [symbol: see text] Be at the repeated batch fermentation process, in the first as well as fourth batch, the better AXAZ-1 gave final [symbol: see text] Be densities of 6.0 and 10.5 respectively, and the baker's yeast 11.6 and 14.5.
TL;DR: For this study, the abundant natural polymers cellulose, starch, and xylan were substituted with acetate to various degrees, and the effect of this modification on the anaerobic biodegradation was assessed using the biochemical methane potential (BMP) protocol.
Abstract: The successful production of novel biodegradable plastic copolymers incorporating both synthetic plastic formulations, such as polystyrene, and naturally occurring biodegradable polymer components, such as cellulose, starch, or xylan, requires stable chemical bonding between these polymers Modification of the natural polymers through acetylation of the available hydroxyl groups permits the formation of appropriate film-forming plastic copolymers However, modification of natural polymers has been demonstrated to result in decreased attack by microbial catalysts For this study, the abundant natural polymers cellulose, starch, and xylan were substituted with acetate to various degrees, and the effect of this modification on the anaerobic biodegradation was assessed using the biochemical methane potential (BMP) protocol Significant reduction in anaerobic biodegradability resulted with all polymers at substitution levels of between 12-17 For the xylan acetate series, the trends for anaerobic biodegradation were in good agreement with reduced enzymatic hydyolysis using commercially available xylanase preparations
TL;DR: In situ cellulase production has the potential to allow cost reductions relative to state-of-the-art process designs on the order of 50¢/gal and high ethanol selectivity for Path 2 corresponds to 90% of this amount.
Abstract: Process development is reviewed for ethanol production from cellulosic biomass via direct microbial conversion (DMC). Experimental data addressing cellulase production and ethanol tolerance are also presented for the candidate DMC organismsClostridium thermocellum andClostridium thermosaccharolyticum. Two potential paths are identified for obtaining organisms for use in DMC. Path 1 involves modification of excellent ethanol producers, so that they also become good cellulase producers; Path 2 involves modification of excellent cellulase producers, so that they also become good ethanol producers. Cellulase production, ethanol tolerance, and ethanol selectivity are considered for both Path 1 and Path 2 organisms. It is concluded thatin situ cellulase production has the potential to allow cost reductions relative to state-of-the-art process designs on the order of 50¢/gal. Based on the data available, the value of cellulase production bythermocellum corresponds to 90% of this amount. However, each process path has a strategic obstacle to be overcome: high-level cellulase expression and secretion for Path 1, and high ethanol selectivity for Path 2. Ethanol tolerance is not seen as a primary factor in choosing between DMC and other ethanol process alternatives.
TL;DR: The incorporated enzyme exhibits high activity and long-term stability over the earlier TCNQ-based glucose sensor, which provides a linear response to glucose over a wide concentration range.
Abstract: Amperometric enzyme electrode for glucose is described based on the incorporation of glucose oxidase (GOD) into graphite paste modified with tetracyanoquinodimethane (TCNQ). The incorporated enzyme exhibits high activity and long-term stability over the earlier TCNQ-based glucose sensor (1). The sensor provides a linear response to glucose over a wide concentration range. The response time of the sensor is 15-50 sec, and the detection limit is 0.5 mM. Stable response to the substrate was obtained during a period of 35 d. Application of the sensor in the plasma analysis is reported.
TL;DR: In this article, the authors show that the best pretreatment conditions are those that produce the highest ethanol yields, which is influenced by the enzymatic digestibility of the pretreated substrate, the xylose yield, and the production of toxic byproducts.
Abstract: The enzymatic digestibility of a pretreated substrate is enhanced by increasing the severity of the pretreatment conditions, apparently because a greater fraction of the hemicellulose sheath surrounding the cellulose is dissolved. This allows the enzyme greater access to the cellulose. However, optimizing enzymatic digestibility will not optimize the production of ethanol. Although increasing the severity of the pretreatment conditions will decrease the remaining xylan, it will also result in the conversion of xylose to furfural. This is a loss of a potential carbon source for conversion to ethanol. The more severe conditions also result in the conversion of more of the cellulose to glucose and subsequent conversion to 5-hydroxymethylfurfural (HMF). Although the digestibility of the pretreated material may be enhanced by the more severe conditions, the conversion of this material to ethanol by yeast may be poor because of the higher levels of furfural and HMF, which are toxic to yeast. The best pretreatment conditions are those that produce the highest ethanol yields, which is influenced by the enzymatic digestibility of the pretreated substrate, the xylose yield, and the production of toxic byproducts.
TL;DR: In this paper, an anaerobic fermentation process was developed to produce calcium magnesium acetate (CMA) from cheese whey, which can be used as a noncorrosive road deicer.
Abstract: A novel, anaerobic fermentation process is developed to produce calcium magnesium acetate (CMA) from cheese whey. CMA can be used as a noncorrosive road deicer. It poses no environmental threats and has many advantages over road salt. A coculture consisting of homolactic and homoacetic bacteria was used to convert whey lactose to lactate and then to acetate in a continuous, immobilized cell bioreactor. The acetate yield from lactose was ~95% (wt/wt) in this homofermentative process. The acetic acid produced from fermentation was recovered in a concentrated CMA solution by using an energyefficient extraction process. The development of a novel, extractive fermentation process to reduce product inhibition and to further increase reactor productivity is also discussed.
TL;DR: An acid protease having milk clotting activity has been isolated from mucor bacilliformis cultures and its instability against heat treatment and its clotting/proteolytic activity ratio indicate that it may be considered as a potential substitute for bovine chymosin.
Abstract: An acid protease having milk clotting activity has been isolated from Mucor bacilliformis cultures. The enzyme was basically purified by ionic exchange chromatography. An average yield of 29 mg purified product was obtained from 100 mL crude extract. As purity criteria, SDS-PAGE, reverse-phase HPLC, and N-terminal analysis were performed. The protease is a protein composed of a single polypeptide chain with glycine at the N-terminus. The mol wt is approx 32,000, and its amino acid composition is very similar to those of other fungal proteases. As expected, its clotting activity was drastically inhibited by pepstatin A action. On the other hand, its instability against heat treatment and its clotting/proteolytic activity ratio indicate that it may be considered as a potential substitute for bovine chymosin.
TL;DR: The biparticle fluidized-bed bioreactor utilizing immobilized microorganisms and adsorbent particles has been shown to enhance the production of lactic acid fourfold in this nonoptimized system.
Abstract: A bioreactor configuration has been tested for simultaneous fermentation and separation of the desired inhibitory product, lactic acid. The bioreactor is a fluidized bed of immobilized Lactobacillus delbreuckii. Another solid phase of denser sorbent particles (a poly-vinyl pyridine resin) was added to this fluidized bed. These sorbent particles fell through the bed, absorbed the product, and were removed. In test fermentations, the addition of the sorbent enhanced the fermentation and moderated the fall of the pH. The biparticle fluidized-bed bioreactor utilizing immobilized microorganisms and adsorbent particles has been shown to enhance the production of lactic acid fourfold in this nonoptimized system.