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۱Effect of Aeration Rate on Biosurfactin Production in a Miniaturized Bioreactor
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اطلاعات انتشار: International Journal Of Environmental Research، ششم،شماره۳، Summer ۲۰۱۲، سال
تعداد صفحات: ۸
Recently, the production of biosurfactants in bioreactors and their use in various pharmaceutical, chemical and food industries have been developed. Optimum production is directly related to the physicochemical condition of culture medium (such as pH and temperature) and engineering parameters of bioreactors (such as aeration rate, volume of operation and the amount of energy input). Understanding the gas transfer in shaken bioreactors equipped with a sterile closure is advantageous to avoid oxygen limitation or carbon dioxide inhibition of a microbial culture. In this study, the effect of aeration rates (due to using different design closures) on the amount of biosurfactin production by Bacillus subtilis ATCC 6633 in a ventilation flask as a miniaturized bioreactor was investigated. The highest biosurfactin concentration (0.0485 g\L\h) was obtained in the optimum conditions in which the amount of filling volume and shaking frequency were 15 ml and 300 rpm, respectively. The specific aeration rate (qin) and maximum oxygen transfer rate (OTRmax), were calculated 1.88 vvm and 0.01 mol\L\h, respectively. The results showed the significant biosurfactin productivity increase under non–oxygen limiting condition.

۲Deletion of RAD52 in Saccharomyces cerevisiae severely decreases frequencies of Agrobacterium genetic transformation mediated by either an integrative or a replicating binary vector
اطلاعات انتشار: Journal of Cell and Molecular Research، چهارم،شماره۲، ۲۰۱۲، سال
تعداد صفحات: ۶
Agrobacterium tumefaciens is capable to transfer genes across kingdoms. It can genetically transform not only plant cells, but also many other bacterial, algal, fungal, animal and human cells. This depends on the interactions among a variety of both Agrobacterium and host genes. Inside the host cell, RAD52 which is involved in DNA repair is a key gene determining integration of T–DNA by homologous recombination. Here, using Saccharomyces cerevisiae haploid strains BY4741 and BY4742, a rad52 diploid deletion strain is constructed in yeast BY4743 background.This model organism was employed to show that RAD52 deletion severely decreases frequencies of Agrobacterium genetic transformation mediated by either an integrative T–DNA or a circular non–integrative T–DNA. Indeed, the frequencies of such Agrobacterium–mediated transformation (AMT) decreased by ca. 25–fold. Hence, host RAD52 deletion might affect AMT by a mechanism which differs from its only involvement in DNA repair in yeast.
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