Utilisation of Jatropha press cake as substrate in biomass and lipase production from Aspergillus niger 65I6 and Rhizomucor miehei CBS 360.62

Jatropha curcas L. is a tropical plant that grows well on poor soils in arid regions and produces oil-rich, unedible seeds. The oil from these seeds can be used in the production of biodiesel. In addition, the press-cake waste that is left after oil extraction contains approximately 40% of protein. The use of Jatropha press-cake as substrate for fungal growth and the production of lipase by Aspergillus niger 65I6 isolated from Indonesia and Rhizomucor miehei CBS 260.62 was investigated. Hydrolysis of the press-cake using 2.5% sodium hydroxide for 45 min was found to be the best pre-treatment method indicated by a high lipase activity. The alkaline hydrolysis increased the amount of reducing sugars and soluble protein to 133.3% and 40% of the initial amount, respectively. 5.7% of the protein fraction was hydrolysed by the alkaline pretreatment. The alkaline hydrolysed Jatropha press-cake was used as a growth substrate for A. niger 65I6 and R. miehei CBS 360.62. Both fungi grew well on the hydrolysed press cake. The addition of glucose or maltodextrin gave a substantial increase in fungal biomass but inhibited the lipase production, very likely due to catabolite repression by the sugars.