Crosses between monokaryons of Pleurotus spp. represent a non-recombinant tool for the improved biotransformation of (+)-valencene to (+)-nootkatone

A. OMARINI; I. PLAGEMANN; S. SCHIMANSKI; U. KRINGS; R.G. BERGER

Campinas

Simposio; 10 SLACA, Latin American Symposium of Food Science; 2013

Biotechnological conversions of low-cost agro-industrial by-products, such as terpenes into more valuable oxygenated derivatives can be achieved using microbial cells or enzymes (Bicas et al., 2009; Uenojo, M., and G. M. Pastore, 2010). In particular, the oxidation of (+)-valencene using Pleurotus sapidus is attractive to obtain the high added-value compound (+)-nootkatone, an impact flavour of grapefruit. The diversity of fungal lifestyles and metabolic pathways presents many opportunities to study facets of eukaryotic biology as well as their biotechnological application. Non-recombinant (classical) genetic approaches represent an option to improve the product yields of fungal biotechnology. Mating of two monokaryotic compatible strains will give rise to a dikaryotic mycelium. In the present work, several hundred monokaryotic (Mk) and new dikaryotic (Dk) strains derived thereof were established from (+)-valencene tolerant strains of P. sapidus. When grouped according to their growth rate on agar plates and compared to the parental Dk of P sapidus, the slowly growing Mks converted (+)-valencene more efficiently to the grapefruit flavour compound (+)-nootkatone. The fast growing Mks and the slow x slow and the fast x fast dikaryotic crosses showed similar or inferior yields. Some slow x fast Dk, however, exceeded the biotransformation capability of the parental Dk significantly. The activity of the responsible enzyme, a recently cloned lipoxygenase, was assayed using the common substrate linoleic acid. No evident correlation with the measured yields of (+)-nootkatone was found indicating that the determination of enzyme activity or mRNA levels may be misleading in assessing the metabolic performance of basidiomycete strains.