Biotransformation of ( R)-(+)- and ( S)-(−)-limonene to α-terpineol by Penicillium digitatum— investigation of the culture conditions

The biotransformation of ( R)-(+)- and ( S)-(−)-limonene by Penicillium digitatum was investigated. One strain of P. digitatum was able to convert ( R)-(+)-limonene to pure ( R)-(+)-α-terpineol in 8 h with a yield of up to 93%. It was found that ( R)-(+)-limonene was converted much better into α-terpineol than ( S)-(−)-limonene, and that no significant chemical conversion of the substrate occurred in control flasks at pH 3.5. The culture conditions involved such as the type and concentration of co-solvent applied and the sequential addition of substrate were investigated, taking into account some findings on the physical behaviour of the system. The highest bioconversion yields were obtained when the substrate was applied as a diluted solution in EtOH.