Abstract
The purpose of the present study was to increase the proteinase activity of the strain NCU116 by combining ultraviolet irradiation and N-methyl-N′-nitro-N-nitroso guanidine treatment, in order to enhance the efficiency of Cinnamomum camphora seed kernel oil (CCSKO) extraction by aqueous enzymatic method (AEM). The mutated strain, designated as NCU116-1, was screened out by the ratio of hydrolytic zone diameter to colony diameter on skim milk plate. The proteinase activity (9116.1 U/ml) of NCU116-1 was increased by 31.9% compared with the parental strain. The extracellular enzymes produced by NCU116-1 included proteinase, pectase, glucoamylase, cellulase and amylase. The proteinase had the maximum activity at 50 °C. Its optimum temperature and pH value were approximately 45 °C and 8.0 respectively. Mn2+ was an activator of neutral proteinase. The glucoamylase had the maximum activity at 35 °C, and was activated by Cu2+, Fe3+ and Mn2+. Its optimum temperatures and pH value were 35 °C and 8.0 respectively. The pectinase had the maximum activity at 40 °C, and was activated by Ca2+ and Mn2+. Its optimum temperatures and pH value were 35–40 °C and 6.0 respectively. The optimum conditions of CCSKO extraction by AEM were also investigated. The results suggested that the best amount of enzyme solution and enzymolysis time were 20% (v/v) and 4 h, respectively. The oil extraction rate was 95.2% under these conditions. Thus, a suitable mutated strain was selected for CCSKO extraction by AEM and the optimum extraction conditions were determined.
Highlights
Cinnamomum camphora (Lauraceae) is a plant with high economic values (Babu et al 2003)
In order to obtain high variability, 80–90% death rates were chosen as a condition for mutagenesis
Thirteen strains with the values of H/C greater than 3.4 were picked from the skim milk bouillon culture medium after N-methyl-N′-nitro-N-nitroso guanidine (NTG) treatment
Summary
Cinnamomum camphora (Lauraceae) is a plant with high economic values (Babu et al 2003). The content of medium chain fatty acid triglyceride (MCT) in Cinnamomum camphora seed kernel oil (CCSKO) was high (MCT > 94%), and MCT was reported to reduce the consumption and subsequent weight gain of animals (Mumme and Stonehouse 2015; Ferreira et al 2013; Wang et al 2016) and improve blood lipid and. The energy consumption of edible oil extraction by AEM was low and the process was safe, which was recognized as ecofriendly technology for extraction of bioactive compounds and reflects the development direction for oil. The product yield by AEM may be increased by using enzymes which can hydrolyse the proteins or other structural components of the seeds. It is imperative to identify the strains which produce a high number of enzymes, have a high yield of proteinase and very low yield of lipase
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