Wheat bran biorefinery: An investigation on the starch derived glucose extraction accompanied by pre- and post-treatment steps

• Glucose of starch fraction of wheat bran was extracted using a conventional method.
• The purity of free glucose in the extract was 44%.
• After a pre-separation of water-solubles the purity of free glucose was enhanced to 58%.
• Hydrothermal treatment of the residual bran did not generate hydroxymethylfurfural.
• Hydrothermal treatment of the residual bran induced an increased level of furfural.

Wheat bran, a side product of the milling industry, can be considered as a feedstock for biorefineries. Unlike other lignocellulosic feedstock, wheat bran contains a reasonable amount of starch, which is not of recalcitrant nature. Therefore, it can be extracted without a costly pretreatment process. The present work evaluates the extraction of starch derived glucose in relation to a wheat bran biorefinery. The purity of free glucose extracted quantitatively was 44%. The extract was concentrated by threefold via nanofiltration, thereby reaching a glucose concentration of 49 g/L. Hydrothermal treatment (180 °C – 20 min) of the starch-free bran did not induce the formation of hydroxymethylfurfural and levulinic acid. Interestingly, the furfural level increased compared to the process, in which bran was treated hydrothermally without a preceding starch extraction. By separation of water-extractables prior to enzymatic hydrolysis, the free glucose purity was increased to 58%, however the yield of glucose decreased to 61%.