Abstract - Improvement of myrosinase activity of Aspergillus sp. NR4617 by chemical mutagenesis

Improvement of myrosinase activity of Aspergillus sp. NR4617 by chemical mutagenesis

Nuansri Rakariyatham
Department of Chemistry, Faculty of Science
Chiang Mai University, Chiang Mai
50200, Thailand
Tel: 66 53 943342
Fax: 66 53 892277
E-mail: nuansri1@yahoo.com

Bordin Butr-Indr*
Division of Clinical Microbiology
Department of Medical Technology
Faculty of Associated Medical Science
Chiang Mai University, Thailand
Tel: 66 15 950578
Fax: 66 53 406294
E-mail: royter99@hotmail.com

Hataichanoke Niamsup
Department of Chemistry, Faculty of Science
Chiang Mai University, Chiang Mai
50200, Thailand
Tel: 66 53 943342
Fax: 66 53 892277
E-mail: Hatahichanok@hotmail.com

Lalida Shank
Department of Chemistry, Faculty of Science
Chiang Mai University, Chiang Mai
50200, Thailand
Tel: 66 53 943342
Fax: 66 53 892277
E-mail: Lalidashank@yahoo.com

*Corresponding author

Keywords: allylisothiocyanate, Aspergillus sp., β-thioglucosidase, myrosinase, EMS mutagenesis, MNNG mutagenesis.

A myrosinase (thioglucoside glucohydrolase or thioglucosidase, EC 3.2.3.147) producing fungus, Aspergillus sp. NR4617, was newly isolated from decayed soil sample obtained in Thailand and was subjected to single exposure to two chemical mutagens, ethyl methanesulfonate (EMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Its myrosinase production was selected on low cost medium prepared from mustard seed cake (Brassica juncea). Studies of production and stability of the enzyme showed that EMS mutagenesis increased myrosinase activity. Aspergillus sp. NR4617E1 produced myrosinase 1.90 U ml^-1 at 36 hrs of the cultivation equivalent to 171% of the enzyme production in wild-type. The stability studies revealed that myrosinase from the mutant strains retained activity similar to wild-type at 30ºC. Aspergillus sp. NR4617E1 degraded 10 mM of glucosinolate completely in 36 hrs. Enhanced myrosinase production and high yields of products (allylisothiocyanate) demonstrated that this mutant could be a new found candidate for feed detoxification and industrial allylisothiocyanate production.