**Mateusz Kutyła, Jan Fiedurek, Anna Gromada, Krzysztof J ˛edrzejewski and Mariusz Trytek \***

Department of Industrial and Environmental Microbiology, Faculty of Biology and Biotechnology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland; mateusz.kutyla@umcs.pl (M.K.); janek@umcs.pl (J.F.); anna.gromada@umcs.pl (A.G.); krzysztof.jedrzejewski@umcs.pl (K.J.) **\*** Correspondence: mariusz.trytek@umcs.pl or mtrytek1@o2.pl; Tel.: +48-81-537-5958

Academic Editor: Josefina Aleu Received: 12 May 2020; Accepted: 1 June 2020; Published: 2 June 2020

**Abstract:** Mutagenesis and adaptation of the psychrotrophic fungus *Chrysosporium pannorum* A-1 to the toxic substrate β-pinene were used to obtain a biocatalyst with increased resistance to this terpene and improved bioconversion properties. Mutants of the parental strain were induced with UV light and *N*-methyl-*N* -nitro-*N*-nitrosoguanidine. Mutants resistant to β-pinene were isolated using agar plates with a linear gradient of substrate concentrations. Active mutants were selected based on their general metabolic activity (GMA) expressed as oxygen consumption rate. Compared to the parental strain, the most active mutant showed an enhanced biotransformation ability to convert β-pinene to *trans*-pinocarveol (315 mg per g of dry mycelium), a 4.3-fold greater biocatalytic activity, and a higher resistance to H2O2-induced oxidative stress. Biotransformation using adapted mutants yielded twice as much *trans*-pinocarveol as the reaction catalyzed by non-adapted mutants. The results indicate that mutagenesis and adaptation of *C. pannorum* A-1 is an effective method of enhancing β-bioconversion of terpenes.

**Keywords:** adaptation; biotransformation; UV/NTG mutagenesis; psychrotrophs; terpenes
