Blakeslea trispora genes for carotene biosynthesis

We cloned the carB and carRA genes involved in beta-carotene biosynthesis from overproducing and wild-type strains of Blakeslea trispora. The carB gene has a length of 1,955 bp, including two introns of 141 and 68 bp, and encodes a protein of 66.4 kDa with phytoene dehydrogenase activity. The carRA gene contains 1,894 bp, with a single intron of 70 bp, and encodes a protein of 69.6 kDa with separate domains for lycopene cyclase and phytoene synthase. The estimated transcript sizes for carB and carRA were 1.8 and 1.9 kb, respectively. CarB from the beta-carotene-overproducing strain B. trispora F-744 had an S528R mutation and a TAG instead of a TAA stop codon. The overproducing strain also had a P143S mutation in CarRA. Both B. trispora genes could complement mutations in orthologous genes in Mucor circinelloides and could be used to construct transformed strains of M. circinelloides that produced higher levels of beta-carotene than did the nontransformed parent. The results show that these genes are conserved across the zygomycetes and that the B. trispora carB and carRA genes are functional and potentially useable to increase carotenoid production.

Biotechnological lycopene production by mated fermentation of Blakeslea trispora

A semi-industrial process (800-l fermentor) for lycopene production by mated fermentation of Blakeslea trispora plus (+) and minus (-) strains has been developed. The culture medium was designed at the flask scale, using a program based on a genetic algorithm; and a fermentation process by means of this medium was developed. Fermentation involves separate vegetative phases for (+) and (-) strains and inoculation of the production medium with a mix of both together. Feeding with imidazole or pyridine, molecules known to inhibit lycopene cyclase enzymatic activity, enhanced lycopene accumulation. Different raw materials and physical parameters, including dissolved oxygen, stirring speed, air flow rate, temperature, and pH, were checked in the fermentor to get maximum lycopene production. Typical data for the fermentation process are presented and discussed. This technology can be easily scaled-up to an industrial application for the production of this carotenoid nowadays widely in demand.

Reduced function of a phenylacetate-oxidizing cytochrome p450 caused strong genetic improvement in early phylogeny of penicillin-producing strains

The single-copy pahA gene from Penicillium chrysogenum encodes a phenylacetate 2-hydroxylase that catalyzes the first step of phenylacetate catabolism, an oxidative route that decreases the precursor availability for penicillin G biosynthesis. PahA protein is homologous to cytochrome P450 monooxygenases involved in the detoxification of xenobiotic compounds, with 84% identity to the Aspergillus nidulans homologue PhacA. Expression level of pahA displays an inverse correlation with the penicillin productivity of the strain and is subject to induction by phenylacetic acid. Gene expression studies have revealed a reduced oxidative activity of the protein encoded by pahA genes from penicillin-overproducing strains of P. chrysogenum compared to the activity conferred by phacA of A. nidulans. Sequencing and expression of wild-type pahA from P. chrysogenum NRRL 1951 revealed that an L181F mutation was responsible for the reduced function in present industrial strains. The mutation has been tracked down to Wisconsin 49-133, a mutant obtained at the Department of Botany of the University of Wisconsin in 1949, at the beginning of the development of the Wisconsin family of strains.