The objective of this research was to improve Glucose-6-phosphate dehydrogenase (G6PD) production by Saccharomyces cerevisiae W303-181, which carry the plasmid YEpPGK-G6PD, by varying the following cultivation conditions: pH value (4.8, 5.7 and 6.6); inoculum concentration (0.1, 0.6 and 1.1 g/L) and initial glucose concentration (20.0, 30.0 and 40.0 g/L). The effect of those variables on G6PD production capability was studied by the application of response surface statistical analysis. The results showed that the highest G6PD production (1594.2 U/L), specific activity (1189.7 U/g cell) and productivity (45.6 U/L.h) occurred at pH 4.8, inoculum concentration of 0.1 g/L and initial glucose concentration of 20.0 g/L, under agitation of 150 rpm at 30ºC after 36 h. In this work, the strain expressed about 21 fold more activity than the wild S. cerevisiae strain, being an attractive and promising new source of this enzyme.

Two-phase aqueous micellar systems can be exploited in separation science for the extraction/purification of desired biomolecules. This article reviews recent experimental and theoretical work by Blankschtein and co-workers on the use of two-phase aqueous micellar systems for the separation of hydrophilic proteins. The experimental partitioning behavior of the enzyme glucose-6-phosphate dehydrogenase (G6PD) in two-phase aqueous micellar systems is also reviewed and new results are presented. Specifically, we discuss very recent work on the purification of G6PD using: i) a two-phase aqueous micellar system composed of the nonionic surfactant n-decyl tetra(ethylene oxide) (C10E4), and (ii) a two-phase aqueous mixed micellar system composed of C10E4 and the cationic surfactant decyltrimethylammonium bromide (C10TAB). Our results indicate that the two-phase aqueous mixed (C10E4/C10TAB) micellar system can improve significantly the partitioning behavior of G6PD relative to that observed in the two-phase aqueous C10E4 micellar system.

This paper describes a novel system which has a great potential for use for extractions in biotechnological processes as it uses only polymers and can be operated at moderate temperatures and salt concentrations. The polymers used in this work are ethylene oxide-propylene oxide 10:90 (w/w) (EO10PO90) and ethylene oxide-propylene oxide 20:80 (w/w) (EO20PO80). The temperature required for thermoseparation decreases with increasing PO content of the copolymer and increasing buffer concentration.

K. marxianus DSM 70106 was cultivated for inulinase production in a medium containing 2.0 g/L of yeast extract, 5.0 g/L of peptone and salts. The addition of corn steep liquor did not increase enzyme production. Inulin, as the main carbon source, afforded higher inulinase production than glucose, fructose, sucrose, lactose, maltose and starch. Glucose, fructose and sucrose reduced enzyme production by 46, 58 and 71%, respectively. By using the best culture medium enzyme activity remained stable for 22 months at 4oC; while at -18oC it decreased by 10%. Maximal activity was found in the pH range of 3.5 to 5.0 and at temperatures from 50 to 60oC. Flocculation was used for cell separation. Shifting the pH was more efficient than using polyelectrolytes, CaCl2, bentonite and Fe2O3. Recovery of inulinase by AOT(sodium di-2-ethylhexyl sulfosuccinate)-reversed micelles yielded up to ~20%.

Hydrolysis of the hemicellulosic fraction of sugarcane bagasse by sulphuric acid was performed in laboratory (25 mL) and semi-pilot (25 L) reactors under different conditions of temperature, time and acid concentration. On the laboratory scale, the three highest recovery yields were obtained at: 140ºC for 10 min with 100 mg acid/g dm (yield=73.4%); 140ºC for 20 min with 100 mg acid/g dm (yield=73.9%) and 150ºC for 20 min with 70 mg acid/g dm (yield=71.8%). These conditions were also used for hydrolysis in a semi-pilot reactor, and the highest xylose recovery yield (83.3%) was obtained at 140ºC for 20 min with 100 mg acid/g dm