Asymmetric synthesis of (S)-ethyl-4-chloro-3-hydroxybutanoate using Candida parapsilosis ATCC 7330

Asymmetric reduction of ethyl-4-chloro-3-oxobutanoate to (S)-ethyl-4-chloro-3-hydroxybutanoate in aqueous medium by resting cells of Candida parapsilosis ATCC 7330 was optimized. The influence of culture parameters (inoculum size, inoculum age and biocatalyst harvest time) and reaction parameters (co-substrate, resting cell, pH and substrate concentrations) on the asymmetric reduction were studied. It was found that these parameters significantly influenced the rate of the asymmetric reduction. Under the optimum conditions, the final concentration of (S)-ethyl-4-chloro-3-hydroxybutanoate, enantiomeric excess and the isolated yield of (S)-ethyl-4-chloro-3-hydroxybutanoate were 1.38 M (230 g/l), >99 and 95%, respectively. The space time yield was 115 mmol/lh, which is significantly higher than other whole cell biocatalysts reported so far.     

Rapid production of ethanol in high concentration by immobilized cells of Saccharomyces cerevisiae through soya flour supplementation

Summary Ethanol concentration and fermentation productivities were substantially increased when soya extract was added to the fermentation medium using immobilized cells of a locally isolated strain of S. cerevisiae. Very high concentrations, 152 and 162 g/l of ethanol, were obtained from a medium containing 300 and 350 g/l sugars respectively by supplementing the medium with soya extract. The fermentation time was also reduced by more than 50%.     

Effect of temperature and pH on immobilized Zymomonas mobilis for continuous production of ethanol

The effects of temperature and inlet pH of the medium on the ethanol productivity and activity of the immobilized Z. mobilis cells during continuous fermentation of glucose have been studied at various temperatures and pH. On changing the temperature from one steady state level to a new one, 6-8 h were required in order to fully experience the effect of a change in temperature; whereas 8-20 h were required on changing the pH. The optimum temperature of 37 degrees C and a broad pH range of 4.4-6.0 were observed for maximum ethanol productivity and ethanol yield.     

Cryptic urokinase binding sites on human foreskin fibroblasts

Human foreskin cells possess sites on their surfaces that specifically bind both active and diisopropylphosphofluoridate-inactivated 2 chain 54 K Da [125I]-urokinase, but do not bind the 54 K Da single chain form of urokinase. 125I-urokinase bound to these sites is not internalized and is very slow to dissociate. There are about 40,000 available binding sites per cell. Brief incubation with pH 2.5 buffer at 5 degrees C unmasks another two to six fold more sites and also extracts plasminogen activator that, based on its accessibility to trypsin, appears to be at the cell surface. This suggests that the cryptic urokinase binding sites could be sites occupied with endogenous plasminogen activator.     

Improvement of inulinase stability of calcium alginate immobilized Kluyveromyces marxianus cells by treatment with hardening agents

To improve the inulinase (2,1-β-d-fructan fructanohydrolase, EC 3.2.1.7) stability of calcium alginate-immobilized Kluyveromyces marxianus cells, treatment with hardening agents has been investigated. Treatment of immobilized cells with some polycationic polymers resulted in little decrease in volumetric reactor productivity, but was most effective in increasing the inulinase stability of the immobilized cells. Inulinase stability of glutaraldehyde-hardened immobilized cells increased two-fold, and for hexamethylenediamine + glutaraldehyde and polyethyleneimine + glutaraldehyde-hardened cells increased six-fold compared with that of the unhardened cells.     

Alkali treatment of corn stover to improve sugar production by enzymatic hydrolysis

Alkali treatment of corn stover improves the avaliability of cellulose and hemicellulose for enzymatic attack. Treatments were carried out for 1 to 60 min at temperatures and NaOH concentrations ranging from 100 to 150 degrees C and 0 to 2%, respectively. Solubilization of the stover and sugar production by enzymatic hydrolysis (Trichoderma viride cellulase) of the solid residue and the dissolved solids were used to measure the effect of caustic treatment. At 150 degrees C and 2% NaOH concentration, 65% of the original stover was dissolved after 5 min and 52% saccharificatin (g sugar/g stover) of the residue and dissolved solids by enzymatic hydrolysis was achieved compared to 20% for untreated corn stover.     

Plant regeneration from cotyledonary node explants of mungbean (Vigna radiata (L.) Wilczek)

Sexually-mature mungbean (Vigna radiata (L.) Wilczek) plants were efficiently regenerated from cotyledonary node explants. The explants were capable of directly developing multiple shoots on basal media devoid of any growth regulators. The shoot multiplication was influenced by media composition, growth regulators, age of donor seedling and explant type. The explants with both the cotyledons attached to the embryonic axis excised from 4-d-old seedlings, produced the highest number of shoots (5 or 6) in 100% of the cultures within 2 weeks on B₅ basal medium (BBM) containing BAP or 2-iP, respectively, (at 5x10^–7M) and 3% sucrose. Shoots elongated and developed better using BAP. Increasing micronutrients, carbohydrate and nitrogen levels in the medium above the original formulation of B₅ basal medium appeared to be of no benefit for increasing the number of shoots. The shoots were rooted on basal MS medium or MS containing 10^–6 of NAA, IAA or IBA. This protocol was found applicable to six other cultivars of mungbean. One hundred rooted shoots were successfully established in soil in the glasshouse, where 90% of them survived. The regenerated plants flowered precociously, but produced normal pods and viable seeds.Abbreviations BAP 6-benzylaminopurine - KIN kinetin - 2-iP 6- — -dimethylallyl aminopurine - AdS adenine sulphate - IAA indole-3-acetic acid - IBA indole-3-butyric acid - NAA 1-naphthalene acetic acid - MS Murashige and Skoog (1962) medium - B₅ Gamborg et al. (1968) medium - C medium MS salts + B₅ vitamins     

Selection and characterization of mannitol-tolerant callus lines of Vigna radiata (L.) Wilczek

An osmotically (mannitol) tolerant callus line of Vigna radiata (L.) Wilczek has been isolated from callus cultures grown on modified PC-L2 medium supplemented with increasing concentrations of mannitol. The tolerance was stable and retained after growth in the absence of mannitol selection for 2 months. The growth of the tolerant line, in the presence of mannitol (540 mol m^-3) was comparable to that of a sensitive callus line growing in the absence of mannitol. This line not only grew well on media containing up to 720 mol m^-3 mannitol, but also required 450 mol m^-3 mannitol for its optimal growth. Osmotically tolerant callus also showed increased tolerance to NaCl (0–250 mol m^-3) stress as compared to sensitive callus. Accumulation of Na⁺ was lower, and the level of K⁺ was more stable in osmotically tolerant than in sensitive calli, when both were exposed to salt. The free proline content of both tolerant and sensitive calli increased on media supplemented with mannitol or NaCl. However, the proline content of sensitive callus was higher than in tolerant callus in the presence of same concentrations of mannitol or NaCl.Abbreviations NAA -naphthaleneacetic acid - 2,4-d 2,4-dichlorophenoxyacetic acid - BAP 6-benzylaminopurine