Jatropha curcas seed cake as substrate for production of xylanase and cellulase by Aspergillus niger FGSCA733 in solid-state fermentation

Jatropha curcas seed-cake was evaluated for use as a solid state fermentation substrate for production of cellulolytic and xylanolytic enzymes by Aspergillus niger. Supplementation of the seedcake with 10% thatch grass (Hyperrhaenia sp.) resulted in a fivefold increase in xylanase production. Ammonium chloride supplementation increased production of xylanase by 13%. Under the same conditions, cellulase production was not influenced by supplementation with grass or the nitrogen sources used. Maximum xylanase was produced at 25 °C whilst cellulase was maximally produced at 40 °C. Highest xylanase activity was obtained when the cultures had an initial pH of 3 whereas cellulase was maximally produced at an initial pH of 5. Under optimised conditions, 6087 U and 3974 U of xylanase and cellulase respectively were obtained per gram of substrate. Zymograms of crude enzyme extracts showed six active bands ranging from 20 kDa to 43 kDa for cellulase and a 31 kDa active band for xylanase.

► The increased demand for renewable sources of fuels has made Jatropha curcas a non-food crop an important crop in the production of biodiesel due to the high oil content of the Jatropha seed.
► Utilisation of the seed cake would add value and economical viability of Jatropha as an oil crop. The utilisation of the seed cake as animal feed is still very limited due to toxicity from a range of antinutritional factors. Detoxification of the seed cake so far has not been viable.
► The results presented in our manuscript demonstrate the potential of the seedcake as substrate in producing high levels of xylanase and cellulase.
► Our findings provide a route to adding value to the Jatropha crop and reducing the cost of industrial enzyme production. The paper generates interest in the use of Jatropha cake in the production of lignocellulolytic enzymes through solid state fermentation. Hence the results presented in this manuscript contribute new knowledge towards the alternative use of Jatropha seed cake as a cheap substrate in fermentation processes for production of industrial enzymes.