Enhanced biosynthetic gene expressions and production of ganoderic acids in static liquid culture of Ganoderma lucidum under phenobarbital induction.

Static liquid culture of Ganoderma lucidum, a traditional Chinese medicinal mushroom, is a proven technology for producing ganoderic acids, which are secondary metabolites that possess antitumor properties. In this work, the addition of phenobarbital, a P450 inducer, was used to enhance the production of total and individual ganoderic acids in a two-stage cultivation involving a period of initial shake flask culture followed by static liquid culture of G. lucidum. The dosage and time of phenobarbital induction were critical for the enhanced production of ganoderic acids. The addition of 100 muM (final concentration) phenobarbital on day 5 after the shake flask culture was converted to the static liquid culture was found to be optimal, resulting in a maximal amount of total ganoderic acids of 41.4 +/- 0.6 mg/g cell dry weight and increases in the levels of ganoderic acid-Mk, -T, -S, and -Me in the treated cells by 47%, 28%, 36%, and 64%, respectively. Meanwhile, the accumulation of lanosterol, a key intermediate, was found to decrease and transcriptions of three key genes encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase, squalene synthase, and lanosterol synthase in the triterpene biosynthetic pathway were up-regulated under phenobarbital induction. This work demonstrated a useful strategy for the enhanced production of ganoderic acids by G. lucidum.

[PKS gene screening based on metagenome of Halichondria rugosa].

Metagenome DNA was extracted from Halichondria rugosa which was collected from South China Sea and kept in -4 degrees C. PKS gene fragment was amplified using PCR with KS domain primers in PKS gene. A DNA fragment about 671bp in length was obtained by PCR. The PCR product was measured by agrose gel electrophoresis. Then the product was recovered from gel and cloned into pUCm-T vector. After that vectors were transformed into competent cells (DH5alpha). PKS gene fragment in positive clones was sequenced. Consequently, the corresponding amino acid sequence was deduced based on nucleotide sequence. BLAST analysis showed that the homology of this amino acid sequence with that deduced from KS domain of PKS gene in Rhodobacterales bacterium was up to 96%. Phylogenetic analysis indicated that the obtained PKS gene belongs to trans-AT KS domains. Meanwhile the result demonstrated the diversity and differences of microorganisms associated with and around sponge in different sea area. It is the first time to find bacterial PKS gene in sponge Halichondria rugosa, which provide powerful proof to the microbial origin hypothesis of sponge active compounds. At the same time, this study lay basis for the utilization of uncultured microorganisms associated with sponge from the aspect of genes.

Favorable effect of very low initial K(L)a value on xylitol production from xylose by a self-isolated strain of Pichia guilliermondii.

Xylitol production from xylose by a self-isolated furfural and 5-hydroxymethyl furfural assimilating Pichia guilliermondii was studied under oxygen limitation. An extremely low initial volumetric oxygen transfer coefficient (0.075 h(-1)) was found most favorable to the xylitol production with yield of 0.61 g g(-1). Related enzymes activities were also investigated and discussed.