Search PubMed⌕ Search

Biomedical subjects

G T Tsao

Publications and source records attributed to G T Tsao.

At least 19 recordsLinked to original sources
PubMed2002

Comparison of fumaric acid production by Rhizopus oryzae using different neutralizing agents.

Fumaric acid fermentation in a 10-L bubble column fermenter using different neutralizing agents [CaCO(3), Ca(OH)(2), NaHCO(3)] by Rhizopus oryzae ATCC 20344 was examined. It was found that in the fermentation using CaCO(3 )as the neutralizing agent the highest fumaric acid weight yield and volumetric productivity were obtained, 53.4% and 1.03 g/L x h(-1) respectively. In the NaHCO(3) case, the fumaric acid weight yield and volumetric productivity were 33.7% and 0.69 g/L x h(-1), respectively, much lower than the CaCO(3) case. However, the NaHCO(3) alternative has advantages of cell reuse and simple downstream processing because of the high solubility of sodium fumarate. These advantages may offset the disadvantages of using NaHCO(3) as the neutralizing agent, and the overall fumaric acid weight yield and volumetric productivity will increase.

Journal Article↗
PubMed2000

Ethanol production from xylose with the yeast Pichia stipitis and simultaneous product recovery by gas stripping using a gas-lift loop fermentor with attached side-arm (GLSA).

The bioconversion of xylose into ethanol with the yeast Pichia stipitis CBS 5773 is inhibited when 20 g/L of ethanol are present in the fermentation broth. In order to avoid this limitation, the fermentation was carried out with simultaneous recovery of product by CO(2) stripping. The fermentation was also improved by attaching a side-arm to the main body of a classical gas-lift loop fermentor. This side-arm increases the liquid circulation, mass transfer, and gas distribution, reducing the amount of oxygen in the inlet gas necessary to perform the fermentation of xylose under microaerobic conditions (K(L)a approximately 16 h(-1)). The continuous stripping of ethanol from the fermentation broth in this new bioreactor system allowed the consumption of higher xylose concentrations than using Erlenmeyer shaker flasks, improved significantly the process productivity and provided a clean ethanol solution by using an ice-cooled condenser system. Finally, a fed-batch fermentation was carried out with a K(L)a = 15.8 h(-1). Starting with 248.2 g of xylose, 237.6 g of xylose was consumed to produce 88.1 g of ethanol which represents 72.6% of the theoretical yield (47.2 g/L of ethanol was recovered in the condenser, while 9.6 g/L remained in the fermentation broth).

Air Movements↗
PubMed2000

A view of the history of biochemical engineering.

The authors present a view of biochemical engineering by describing their personal interests and experience over the years involving mostly conversion of lignocellulosics into fuels and chemicals and the associated engineering subjects.

Animals↗
PubMed2000

Repeated solid-phase fermentation and extraction for enzyme production.

Solid-phase fermentation has been found to have a much higher productivity than the popular liquid submerged fermentation in producing cellulase enzymes. The highest reported productivity in the literature for cellulases by Trichoderma cultures in submerged fermentation is 158 filter paper units (FPU)/(h.L) of fermenting liquid. From preliminary experiments of solid-phase fermentation in 1000-mL flasks, a productivity of 234 FPU of cellulases/(h.L) of solid-bed volume was obtained. When two novel techniques--pressure pulsation and repeated extraction--were applied, a productivity of 806 FPU/(h.L) was achieved. The same techniques also greatly enhanced the productivity of other enzymes by fungal cultures in solid-phase fermentation.

Biotechnology↗
PubMed2000

Coproduction of ethanol and glycerol.

Ethanol and glycerol are both metabolic products of yeasts. There are occasions when coproduction of both is considered desirable in industrial operations. In this article, we describe the potential of integrating the two processes. A LORRE Y8 yeast culture isolated from molasses is capable of efficient glycerol production from glucose, and a yeast Culture 1400 is an excellent producer of ethanol. By controlling the process conditions, the ratio of ethanol and glycerol production can be varied.

Bioreactors↗
PubMed2000

Solid-state fermentation with Aspergillus niger for cellobiase production.

Aspergillus niger NRRL3 was cultivated in a moist wheat bran and ground corncob solid medium supplemented with inorganic minerals for the production of cellobiase (beta-1,4-glucosidase, EC 3.2.1.21). With this method, A. niger NRRL3 was able to produce a high concentration of cellobiase (215 IU/g of solid substrate) after 96 h of incubation. Temperature and moisture content affected final cellobiase titers. The best conditions for cellobiase production from solid substrate by A. niger NRRL3 were determined to be 70% moisture and 35 degrees C.

Aspergillus↗
PubMed2000

Mycelial pellet formation by Rhizopus oryzae ATCC 20344.

Factors in a cultivation medium affecting fungal growth morphology and fumaric acid production by Rhizopus oryzae ATCC 20344 were investigated. These factors included the initial pH value and trace metals such as zinc, magnesium, iron, and manganese in the cultivation medium. It was found that a significant change in the growth morphology of R. oryzae ATCC 20344 occurs when the initial pH value is varied. A lower initial pH value in the cultivation medium was inhibitory to fungal growth, and fast growth in the cultivation medium at a higher initial pH value promoted the formation of large pellets or filamentous forms. Trace metals in the cultivation media also had significant effects on pellet formation and fumaric acid fermentation.

Cations, Divalent↗
PubMed1999

Production of multifunctional organic acids from renewable resources.

Recently, the microbial production of multifunctional organic acid has received interest due to their increased use in the food industry and their potential as raw materials for the manufacture of biodegradable polymers. Certain species of microorganisms produce significant quantities of organic acids in high yields under specific cultivation conditions from biomass-derived carbohydrates. The accumulation of some acids, such as fumaric, malic and succinic acid, are believed to involve CO2-fixation which gives high yields of products. The application of special fermentation techniques and the methods for downstream processing of products are described. Techniques such as simultaneous fermentation and product recovery and downstream processing are likely to occupy an important role in the reduction of production costs. Finally, some aspects of process design and current industrial production processes are discussed.

Aspartic Acid↗
PubMed1999

Ethanol production from renewable resources.

Vast amounts of renewable biomass are available for conversion to liquid fuel, ethanol. In order to convert biomass to ethanol, the efficient utilization of both cellulose-derived and hemicellulose-derived carbohydrates is essential. Six-carbon sugars are readily utilized for this purpose. Pentoses, on the other hand, are more difficult to convert. Several metabolic factors limit the efficient utilization of pentoses (xylose and arabinose). Recent developments in the improvement of microbial cultures provide the versatility of conversion of both hexoses and pentoses to ethanol more efficiently. In addition, novel bioprocess technologies offer a promising prospective for the efficient conversion of biomass and recovery of ethanol.

Biomass↗
PubMed1999

Fermentation kinetics of ethanol production from glucose and xylose by recombinant Saccharomyces 1400(pLNH33).

Fermentation kinetics of ethanol production from glucose, xylose, and their mixtures using a recombinant Saccharomyces 1400(pLNH33) are reported. Single-substrate kinetics indicate that the specific growth rate of the yeast and the specific ethanol productivity on glucose as the substrate was greater than on xylose as a substrate. Ethanol yields from glucose and xylose fermentation were typically 95 and 80% of the theoretical yield, respectively. The effect of ethanol inhibition is more pronounced for xylose fermentation than for glucose fermentation. Studies on glucose-xylose mixtures indicate that the recombinant yeast co-ferments glucose and xylose. Fermentation of a 52.8 g/L glucose and 56.3 g/L xylose mixture gave an ethanol concentration of 47.9 g/L after 36 h. Based on a theoretical yield of 0.51 g ethanol/g sugars, the ethanol yield from this experiment (for data up to 24 h) was calculated to be 0.46 g ethanol/g sugar or 90% of the theoretical yield. The specific growth rate of the yeast on glucose-xylose mixtures was found to lie between the specific growth rate on glucose and the specific growth rate on xylose. Kinetic studies were used to develop a fermentation model incorporating the effects of substrate inhibition, product inhibition, and inoculum size. Good agreements were obtained between model predictions and experimental data from batch fermentation of glucose, xylose, and their mixtures.

Journal Article↗
PubMed1999

Optimization of L-lactic acid production from glucose by Rhizopus oryzae ATCC 52311.

The effect of nutrients on L(+)-lactic acid production from glucose was investigated using Rhizopus oryzae ATCC 52311. From the shake-flask experiments, the optimal medium composition was defined for improved lactic-acid production. In order to enhance lactic-acid production rate and product yield, controlled aeration in a bubble column was conducted under optimal conditions. Results showed a maximum lactic-acid production rate of 2.58 g/L/h was obtained with an initial glucose concentration of 94 g/L. Final lactic-acid concentration of 83 g/L was achieved after 32 h of fermentation with a weight of 0.88 g lactic acid/g glucose consumed.

Journal Article↗
PubMed1998

Production of L-malic acid via biocatalysis employing wild-type and respiratory-deficient yeasts.

The yeast Saccharomyces cerevisiae has been used to efficiently produce L-malic acid from fumaric acid. Fumarase is responsible for the reversible conversion of fumaric and L-malic acids in the TCA cycle. To investigate the function of mitochondrial and cytoplasmic fumarase isoenzymes in L-malic acid bioconversion, a wild-type strain and a cytoplasmic respiratory-deficient mutant devoid of functional mitochondria were employed. The mutant strain, which only contained the cytoplasmic fumarase, was still functional in fumaric acid to L-malic acid bioconversion However, its specific conversion rate was much lower (0.20 g/g.h) than that of the wild-type strain (0.55 g/g.h).

Catalysis↗
PubMed1998

Bioconversion of fumaric acid to succinic acid by recombinant E. coli.

Succinic acid was produced efficiently from fumaric acid by a recombinant E. coli strain DH5 alpha/pGC1002 containing multicopy fumarate reductase genes. The effects of initial fumaric acid and glucose concentration on the production of succinic acid were investigated. Succinic acid reached 41 to over 60 g/L in 48.5 h starting with 50 to 64 g/L fumaric acid. Significant substrate inhibition was observed at initial fumaric acid concentration of 90 g/L. L-Malic acid became the major fermentation product under these conditions. Provision of glucose (5-30 g/L) to the fermentation medium stimulated the initial succinic acid production rate over two folds.

Acetic Acid↗
PubMed1996

Pretreatment of sugar cane bagasse hemicellulose hydrolysate for xylitol production by yeast.

A total of six known xylitol-producing yeast strains were screened for production of xylitol from xylose. Candida sp. 11-2 proved to be the best producer. It was chosen to study its ability to produce xylitol from hemicellulose hydrolysate derived from sugar cane bagasse. The hydrolysate was prepared by dilute sulfuric acid (2-3% [w/v]) hydrolysis, with a high-solid, low-liquid ratio followed by leaching. Owing to the inhibitors present in the hydrolysate, different treatments were studied to overcome its effect. In order to reach higher xylitol productivity, treated hydrolysates were concentrated by vacuum evaporation in rotavapor to provide a higher initial xylose concentration. After treatment, Candida sp. 11-2 was able to ferment xylose in hemicellulose hydrolysate to produce xylitol.

Charcoal↗
PubMed1996

Improvement of productivity of yeast cell with a novel airlift loop reactor.

Two different strains of baker's yeast are cultivated using a fed-batch process with a novel airlift loop reactor. The reactor can be operated not only under steady-state conditions as the traditional airlift loop reactor, but also under forced periodically operational conditions in which the direction of liquid circulating flow is alternatively changed. Compared with the traditional steady-state operation, both the growth rate and yield of cells are much higher in the forced periodic operation.

Biotechnology↗
PubMed1996

Simultaneous Production and Recovery of Fumaric Acid from Immobilized Rhizopus oryzae with a Rotary Biofilm Contactor and an Adsorption Column.

An integrated system of simultaneous fermentation-adsorption for the production and recovery of fumaric acid from glucose by Rhizopus oryzae was investigated. The system was constructed such that growing Rhizopus mycelia were self-immobilized on the plastic discs of a rotary biofilm contactor during the nitrogen-rich growth phase. During the nongrowth, production phase, the biofilm was alternately exposed to liquid medium and air upon rotation of the discs in the horizontal fermentation vessel. The product of fermentation, fumaric acid, was removed simultaneously and continuously by a coupled adsorption column, thereby moderating inhibition, enhancing the fermentation rate, and sustaining cell viability. Another beneficial effect of the removal of fumaric acid is release of hydroxyl ions from a polyvinyl pyridine adsorbent into the circulating fermentation broth. This moderates the decrease in pH that would otherwise occur. Polyvinyl pyridine and IRA-900 gave the highest loading for this type of fermentation. This fermentation system is capable of producing fumaric acid with an average yield of 85 g/liter from 100 g of glucose per liter within 20 h under repetitive fed-batch cycles. On a weight yield basis, 91% of the theoretical maximum was obtained with a productivity of 4.25 g/liter/h. This is in contrast to stirred-tank fermentation supplemented with calcium carbonate, whose average weight yield was 65% after 72 h with a productivity of 0.9 g/liter/h. The immobilized reactor was operated repetitively for 2 weeks without loss of biological activity.

Journal Article↗
PubMed1990

Purification, characterization, and amino terminal sequence of xylose reductase from Candida shehatae.

D-Xylose is a major component of the carbohydrates derived from agricultural residues and forest products. Among more than two hundred known xylose-utilizing yeasts, only a few species are known to be able to ferment xylose anaerobically. Candida shehatae is one of such xylose-fermenting yeasts. Xylose reductase (E.C. 1.1.1.21) is a key enzyme responsible for xylose metabolism in xylose-utilizing as well as xylose-fermenting yeasts. In this paper, we report the development of a convenient and reliable procedure for the purification of xylose reductase from C. shehatae to near homogeneity. The amino acid composition and N-terminal sequence of the enzyme have also been analyzed. C. shehatae seems to contain only a single xylose reductase, but the enzyme has a dual coenzyme specificity for both NADPH and NADH. The enzyme is remarkably stable at room temperature and 4 degrees C.

Aldehyde Reductase↗