Studies on the catalytic performance of lignin peroxidase in nonionic reversed micelles / 生物工程学报

Lignin peroxidase (LiP) hosted in Brij 30/cyclohexane/water nonionic reversed micelle could express its catalytic activity, but in Triton X-100/n-pentanol/cyclohexane/water nonionic reversed micelle LiP didn't show any catalytic activity. Some key factors that affected the catalytic activity of LiP in Brij 30 reversed micelle were studied at 20 degrees C. The optimum conditions were:omega0 = 8.5, pH = 2.2, [Brij30] = 600 mmol/L; under these conditions the half time of LiP was ca. 50 hours. As compared with the properties of LiP in aqueous solution, the activity of LiP hosted in Brij 30 reversed micelle dropped, but its stability improved greatly. To reveal the role of normal alcohol, which was a necessary component for forming Triton X-100 reversed micelles, the effect of n-pentanol on the catalytic activity of LiP in Brij 30 reversed micelle was investigated. Results indicated that high concentration of the alcohol deactivated LiP. So it was deduced that the phenomenon that LiP hosted in the Triton X-100 reversed micelles could not express its activity was mainly due to the alcohol co-surfactant.

Progress in the pathway engineering of ethanol fermentation from xylose utilising recombinant Saccharomyces cerevisiae / 生物工程学报

Pathway engineering was the third generation of gene engineering. Its main goals were to change metabolic flux and open a new metabolic pathway in organism. Application of recombinant DNA methods to restructure metabolic networks can improve production of metabolite and protein products by altering pathway distributions and rates. Ethanol is the most advanced liquid fuel because it is environmentally friendly. Enhancing fuel ethanol production will require developing lower-cost feedstock, and only lignocellulosic feedstock is available in sufficient quantities to substitute for corn starch. Xylose is the major pentose found in lignocellulosic materials and after glucose the most abundant sugar available in nature. Recently a lot of attentions have been focused on designing metabolic pathway of Saccharomyces cerevisiae in order to expand the substrate of ethanol fermentation, because it is a traditional ethanol producing strain and has wonderful properties for ethanol industry. However, it can not utilize xylose but convert the isomer, xylulose. Many attempts are based on introducing the genes in the pathway of xylose metabolism. The further research includes overexpressing the key enzyme or decreasing the unimportant flux. The sugars in lignocellulose hydrolyzates, therefore, could be efficiently utilized. Here, we describe the ethanol pathway engineering progress in ethanol fermentation from xylose with recombinant Saccharomyces cerevisiae.

Hydrogen photoproduction from acetate by Rhodopseudomonas palustris / 生物工程学报

Based on the characteristics of metabolism of photosynthetic bacteria and the major kinds of organic compounds produced in wastewater degradation, eleven kinds of organic compounds were chosen for hydrogen photoproduction using Rhodopseudomonas palustris Z strain. The maximal volumetric H2 productivity was obtained using acetate as the sole carbon source and electron donor. The kinetics of cell growth and H2 liberation, and the influences of several major limiting factors on photoevolution of H2 were examined using acetate as carbon source. It was shown that hydrogen production was partially correlated with cell growth. The medium composition of the preculture, the preculture time, and inoculation volume were confirmed to have big effects on hydrogen photoevolution. The time delay of H2 production was evidently shortened using the inoculum of late exponential growth phase or stationary phase using ammonium sulfate as nitrogen source or with the inoculum of middle exponential growth phase using glutamate as the nitrogen source. The identity of temperature and light intensity for H2 evolution and cell growth has significant potential application in the technology of splitting organic acid into H2 by photosynthetic bacteria. The concentrations of acetate and glutamate in the medium affected hydrogen photoevolution and cell growth significantly. The productivity of H2 increased with substrate concentrations when substrate concentrations of sodium acetate and sodium glutamate were lower than 70 mmol/L and 15 mmol/L, respectively. Hydrogen production was inhibited but the cell growth was faster when the concentration of sodium glutamate over 15 mmol/L due to forming free NH4+. The highest rate of hydrogen production was 19.4 mL.L-1.h-1 using 30 mmol/L of sodium acetate as hydrogen donor under the standard conditions, respectively. The optimal conditions for hydrogen production were 35-37 degrees C, 6000-8000 lx and pH 7.3-8.3. The effects of oxygen and inoculation volume on photoproduction of hydrogen were also discussed.

Application of Response Surface Analysis (RSA) in Fermentation Condition Optimization of Penicillium decumbens Ju-A_(10) for CMCase Production / 微生物学通报

Fermentation condition optimization of P. decumbens Ju-A10 for production of CMCase using three kinds of plant cellulosic wastes as carbon sources was made using RSA method. The result was that CMCase was the highest when the level of carbon source was 9. 77 % , 8. 69 % and 9. 97% , and liquid volume was 64. 7 mL, 54. 2 mL, 40. 8 mL for carbon sources of millet straw, wheat straw and paper sludge, respectively. The value of CMCase was 29. 26IU/mL, 29. 14 IU/mL, 29. 81 IU/mL, respectively, in the above cases. The value of R2 is 0. 9117 , 0. 9246, 0. 8655 , respectively. It could be concluded that the fermentation models were quite reliable. The method can be applied in optimization of fungi fermentation medium.

SCREENING OF STRAINS PRODUCING EXTRACELLULAR MELANIN / 微生物学通报

The growth and pigment production of 47 strains on casein medium were studied comparatively.T4 and Neurospora crassa AS 3.1602 were selected for their capacity of producing melanin on five different culture media. Melanin produced by T4 was investigated, and T4 was identified as Proteus mirabilis primarily.

STUDY ON LIQUID CONDITIONS IN SHAKING FLASKS FOR LACCASE PRODUCTION BY A WHITE ROT FUNGUS / 微生物学通报

A white-rot fungi Rigidoporus sp.W-1 which could produce laccase was isolated. The fermentation conditions in shaking flasks were investigated. The optimal carbon source was wheat bran and (NH 4) 2SO 4 was the optimal nitrogen source. The components of the medium were optimized by orthogonal experiment. When W-1 was cultured under the optimum conditions, the activity of laccase could get to 7.1U/mL in 7 days.A great amount of crude laccase could be obtained by adding fresh medium to the 7 days old mycelium.

SCREENING OF STRAINS PRODUCING LIPASES WITH HIGH ACTIVITIES AND CONSTRUCTION OF STRAIN LIBRARY / 微生物学通报

More than 80 strains producing lipases were screened from oily soil of vegetable oil plant, meat processing factory and dairy factory in Jinan city, Shandong Province, which included bacteria, moulds and yeast. Conditions for lipase production and properties of some enzymes were studied. One drug-resistant mutant strain Y-11 with higher lipase activity was from Trichosporon sp. Y-1. In addition, Optimization of lipase production and characterization of enzymes were carried out. On the basis of above experiments, a characteristic library of stains producing lipases was established.

A NOVEL STRATEGY FOR SCREENING MUTANT ENZYMES UNDER NON-GROWTH CONDITIONS / 微生物学通报

The technique of double-layered plate was developed for screening the library of mutant endoglucanase III from Trichoderma reesei generated by the method of directed evolution.The enzyme activity was determined according to the velocity of the formation of halos on the plates.Several mutants with higher activity than the wild type at low temperature or alkaline pH were obtained by using this strategy under different screening conditions.Further results of spectrophotometric determination of the activities of these mutants were consistent with the results of plate screening.The establishment of such strategy will broaden the applications of the directed evolution methods for improving the existing proteins to obtain useful enzymes with new properties for industrial applications.