Impact of structure and composition of different sorghum xylans as substrates on production of xylanase enzyme by Aspergillus fumigatus RSP-8

Xylan composition from six different bmr sorghum (Sorghum bicolor L.) biomasses (Atlas 12, BN 612, Atlas 3986, IS 27333, Atlas N598 & IS 27206) with variable lignin content were analyzed for their structure and evaluated as a substrate for xylanase complex production using Aspergillus fumigatus RSP-8. Chemical compositional analysis of xylans revealed that all the xylans belong to arabinoxylan (AX) type and are composed of xylose, glucose, and arabinose in varying concentrations. The relative content of xylose varied from 90 % (of total sugars) in the variety IS 27206 to 72 % in Atlas N598. Atlas N598 xylan contained the highest relative glucose content of 22 % and the least content was observed in IS 27206 xylan (2.9 %). The relative content of L-arabinose was constant with fewer variations (5.1-6.7 %). FT-IR analysis showed that the xylans extracted from different sorghum substrates varied in structure. The spectra of all the xylans exhibited absorption maxima of similar to 895 cm(-1) which is characteristic for the beta-(1 4) xylans. The strongest absorption bands in the IR spectra were observed at 3700-3000 and 1200-1000 cm(-1) with varying intensities. Xylanase production revealed that the source of xylan significantly affected the fungal growth and xylanase productivity. The highest xylanase production (1248 U/ mL) and fungal biomass dry weight (5.94 g/L) was observed with IS 27206 xylan and the least productivity of 964 U/mL and fungal biomass dry weight (3.74 g/L) with Atlas N598 xylan noticed as substrate.