Cascade processing of wheat bran through a biorefinery approach

Abstract

Structural characteristics of wheat bran such as surface area, crystallinity, cellulose, hemicellulose, and lignin content significantly affect the yield of biorefinery products such as protein, fermentable sugar and lignin. The aim of the study was to use a sequence of high pressure extraction and hydrolysis processes in a cascade to create high potential value added products, namely, proteins, fermentable sugars and lignin. In the present study, four different sets of experiments were carried out step by step in a cascade sequence. The main experiments were the sequential extraction and hydrolysis which were optimized using design of experiments. Protein extraction from wheat bran was performed in a fixed bed reactor and was maximized to 1.976g/L at the elicited optimum conditions which were 80°C, pH 9.3 for a duration of 30min. In the sequential experiment, process parameters such as temperature, flow rate and duration were optimized for liquid hot water (LHW) hydrolysis. The maximum reducing sugar concentration was 200g/kg which corresponded to 34% per dry biomass obtained at a flow rate of 5ml/min, temperature of 210°C during a 45min treatment. The following step was enzymatic hydrolysis to saccharify the cellulose under high pressure, where the independent variables were pressure, temperature and process time in order to ascertain the process conditions maximizing the reducing sugar content, where a positive correlation was observed between the solid–liquid loading ratio and reducing sugar yield. In the final step, the lignin content of all analyzed lignin fraction was found 70% (w/w).