Studies on effects of water temperature, stocking density and feeding cycle on growth and feeding in Hirudo nipponica / 中国中药杂志

Effects of different water temperature, stocking density and feeding cycle on growth, feeding and survival of Hirudo nipponica have been studied, six temperature gradients were set: 18, 22, 26, 30, 34 and 38 ℃, five stocking density gradients were set: 30, 60, 120, 180 and 240 leech/L, four feeding cycle gradients were set: 2, 5, 10 and 20 d, respectively. The results showed that there exists a significant regression relationship between water temperature and specific growth rate: y=-0.016 5x²+0.836 9x-6.847 5（R²=0.990 8）（P<0.05）, a regression analysis indicated that specific growth rate reached the maximum (3.76) at 25.36 ℃. When water temperature was beyond 30 ℃, the survival rate significantly decreased as water temperature increased （P<0.05）. The specific growth rate and survival rate decreased as stocking density increased. A linear relationship exists between the feeding cycle and the SGR: y=-0.094 1x+3.832 9（R²=0.992 7）. From this study, it can be concluded that the optimal water temperature and stocking density for the growth of H. nipponica is 22-26 ℃ and 30-120 leech/L, respectively.

High RNA accumulation in Candida tropicalis is affected by specific growth rate and different medium composition / 中国药科大学学报

Batch and continuous fermentation were adopted to investigate the effect of specific growth rate and amino acid components on RNA accumulation in Candida tropicalis ATCC 20408 in fermentation medium ( FM), yeast peptone dextrose medium (YPD), molasses fermentation medium ( MFM) and FM without corn steep liquor. The data showed that obvious differences in intracellular RNA accumulation were observed at different cell growth phases in bath fermentation prosess, and RNA level reached 11. 8% (g-RNA /g-DCW) during exponential phase, and only 6.9% during stationary phases. It was also found that intracellular RNA accumulation increased with the increase of specific growth rate in continue fermentation prosess, and the highest RNA level reached 15. 6% with the glucose conversion rate of 42. 8% at the dilution rate of 0. 5 h-1. Furthermore, the data showed that RNA lever was notably increased in batch fermentation process when amino acids or peptone was added into the fermentation medium containing no corn steep liquor. Taken together, it was reported for the first time that specific growth rate and amino acid components plays a leading role on the intracellular RNA accumulation in C. tropica lis, and specific growth rate is more important.

Optimization of feeding strategy for the ergosterol production by yeasts saccharomyces cerevisiae / Optimización de la estrategia de alimentación para la producción de ergosterol por levaduras saccharomyces cerevisiae

Objective of this study was to optimize ergosterol production by yeast strain Saccharomyces cerevisiae with the use of computer controlled feeding of cultivation medium. Baker´s yeasts strain of Saccharomyces cerevisiae originally modified and selected as mutant D7 was further applied in an industrial scale and also in this investigation. Composition of cultivation medium was optimized with the use of a modified Rosenbrock´s method with regard to following components: glucose, yeast extract, ammonium sulphate, potassium dihydrogen phosphate, magnesium sulphate and calcium chloride. Cultivation of yeast culture was performed in 7 L laboratory bioreactor with a working volume of 5 L equipped with a control unit and linked to a computer, with dissolved oxygen tension measurement, oxygen and carbon dioxide analyzers. BIOGENES prototype software was created from the commercial control system Genesis for Windows 3.0 (GFW), from Iconics and CLIPS 6.04 for the PC-Windows platform. From various factors affecting sterol biosynthesis a specific growth rate was chosen. Feed rate was controlled according to mathematical model. In this case it dealt with a design of optimal profile of specific growth rate with consequent calculation of carbon dioxide profile. Sterol concentration in the dry biomass increased from 1.0 % up to 3 %.

El objetivo de este estudio fue optimizar la producción de ergosterol por una cepa de levadura Saccharomyces cerevisiae, controlando la alimentación de medio de cultivo por computadora. La cepa de levadura panadera Saccharomyces cerevisiae originalmente modificada y seleccionada como mutante D7 fue posteriormente utilizada a escala industrial y también para esta investigación. La composición del medio de cultivo fue optimizada usando el método modificado de Rosenbrock respecto a los siguientes componentes: glucosa, extracto de levadura, sulfato de amonio, fosfato dihidrógeno de potasio, sulfato de magnesio y cloruro de calcio. El cultivo de las células de levadura se llevó a cabo en un biorreactor de laboratorio de 7L con un volumen de trabajo de 5L, equipado con una unidad de control conectada a una computadora, con medición de la tensión de oxígeno disuelto y analizadores de oxígeno y dióxido de carbono. Un software prototipo BIOGENES fue creado a partir del sistema de control comercial Genesis para Windows 3.0 (GFW), de Iconics y CLIPS 6.04 para la plataforma de PC-Windows. A partir de varios factores que afectan la biosíntesis de esterol se escogió una tasa específica de crecimiento. La tasa de alimentación se controló mediante un modelo matemático. En este caso, se trató con un diseño de perfil óptimo de tasa de crecimiento específico con un consecuente cálculo del perfil de dióxido de carbono. La concentración de esterol en la biomasa seca se incrementó desde 1,0% hasta 3%.

Submerged culture conditions for the production of mycelial biomass and antimicrobial metabolites by Polyporus tricholoma Mont. / Condições de cultivo em meio líquido para produção de biomassa e metabólitos antibacterianos por Polyporus tricholoma Mont.

Basidiomycete fungi of the Polyporus genus are a source of secondary metabolites which are of medicinal interest as antibacterial compounds. As these substances are produced in a small amount by the fungi, the study of the cultivation conditions in vitro that could possibly optimize their production seems of major importance. The effects of glucose and lactose, pH and agitation on biomass concentration and on the specific growth rate caused by the basidiomycete Polyporus tricholoma were investigated. The initial pH (4.5, 6.5 and 8.5) was autoregulated at pH 5.5, and the agitation increased the mycelial growth and the specific growth rate. The high concentration of carbon sources (4 percent) increased biomass production. The lactose concentration and the absence of agitation were determinant in the production of antibacterial metabolites. The characterization of the antibacterial substance by GC-MS indicated a major compound, isodrimenediol, produced by the fungus Polyporus tricholoma with activity against Staphylococcus aureus.

Os fungos basidiomicetos do gênero Polyporus são fonte de metabólitos secundários de interesse medicinal como os compostos antibacterianos. Como estas substâncias são produzidas em pequenas quantidades pelos fungos, o estudo de condições de cultivo in vitro que otimizem sua produção, é de fundamental importância. Os efeitos da glicose e lactose, pH e agitação na concentração da biomassa e na velocidade específica de crescimento realizada pelo basidiomiceto Polyporus tricholoma foram investigados. O pH inicial (4.5, 6.5 e 8.5) foi autoregulado para pH 5.5, e a agitação aumentou o crescimento micelial e a velocidade específica de crescimento. A maior concentração das fontes de carbono (4 por cento) incrementou a produção de biomassa. A concentração de lactose e a ausência de agitação foram determinantes na produção dos metabólitos antibacterianos. A caracterização da substância antibacteriana por CG-EM mostrou como componente majoritário o isodrimenediol, produzido pelo fungo Polyporus tricholoma, com atividade contra Staphylococcus aureus.

Effect of Specific Growth Rate and Nitrogen Source on the Production of Recombinant Lateolabrax japonicus Growth Hormone by Pichia pastoris / 微生物学通报

The bioreactor production of recombinant Lateolabrax japonicus growth hormone (rljGH) expressed intracellularly by Pichia pastoris was investigated. A strategy of feeding methanol at the exponential rate was established and the effect of specific growth rate on the rljGH production was examined. The results indicated that the average specific production rate increased and the rljGH production duration decreased as the specific growth rate increased. The maximum specific rljGH production (0.58 mg/g WCW) was achieved at a specific growth rate of 0.029/h. The effect of supplementing ammonium sulfate, peptone and yeast ex- tract on the rljGH production was further investigated. The results indicated that the effects of ammonium sulfate and peptone were not significant. Supplementing yeast extract of 2.5 g/L was advantageous for the rljGH production. The duration of the rljGH production was increased to 23 h from 17 h and the fermenta- tion stability of run-to-run could be improved.