The interactions between the ammonium assimilatory pathways and b-lactam production were investigated by disruption of the NADPH-dependent glutamate dehydrogenase gene (gdhA) in two industrial b-lactam-producing strains of Penicillium chrysogenum. The strains used were an adipoyl-7-ADCA-and a penicillin-producing strain. The gdhA gene disruption caused a decrease in maximum specific growth rate of 26 % and 35 % for the adipoyl-7-ADCA-producing strain and the penicillin-producing strain, respectively, compared to the corresponding reference strains. Interestingly, no b-lactam production was detected in either of the DgdhA strains. Supplementation with glutamate restored growth but no b-lactam production was detected for the constructed strains. Cultures with high ammonium concentrations (repressing conditions) and with proline as nitrogen source (de-repressed conditions) showed continued b-lactam production for the reference strains whereas the DgdhA strains remained non-productive under all conditions. By overexpressing the NAD-dependent glutamate dehydrogenase, the specific growth rate could be restored, but still no b-lactam production was detected. The results indicate that the NADPH-dependent glutamate dehydrogenase may be directly or indirectly involved in the regulation of b-lactam production in industrial strains of P. chrysogenum.

No abstract

No abstract

Genetic and biochemical approaches reveal the existence of a Q-linolenic acid biosynthetic pathway in Mucor rouxii. By treatment with ultraviolet light, combined with low temperature cultivation and filtration enrichment, a mutant defective in polyunsaturated fatty acid synthesis was isolated. Genetic analysis and fatty acid supplementation indicate that the defect occurred in the v 12 -desaturation resulting in the absence of cis-linoleic acid and Q-linolenic acid and in the accumulation of monounsaturated fatty acids. In addition, an unusual fatty acid, trans-linoleic acid (9c,12t-C18:2), which has not been reported previously in this fungus, was found to increase in the mutant. The information gained from the mutant was used to develop the hypothetical pathway of fatty acid desaturation in M. rouxii.