Submitted to: Bioresource Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/20/2012
Publication Date: 3/1/2012
Publication URL: http://handle.nal.usda.gov/10113/56458
Citation: Chen, R., Yuea, Z., Deitza, L., Liu, Y., Mulbry III, W.W., Liao, W. 2012. Use of an algal hydrolysate to improve enzymatic hydrolysis of anaerobically digested fiber. Bioresource Technology. 108:149-154. Interpretive Summary: Algae have attracted attention for over five decades as a promising feedstock for biofuels production. Of particular interest is the coupling of algae-based wastewater treatment processes with conversion of the algal byproduct into complementary products (such as biofuels, chemicals, and fertilizers). The general goal of this research project was to evaluate potential bioenergy uses of sugars from wastewater-grown algae. One specific goal was to determine the optimal conditions needed to break apart algal cells in order to release algal sugars and proteins. An additional goal was to determine whether algal sugars and proteins would be helpful as additives in reactions with other biofuel feedstocks. These results will be useful for scientists and engineers involved in designing improved methods for producing biofuels.
Technical Abstract: This study investigated the use of acid hydrolyzed algae to enhance the enzymatic hydrolysis of cellulosic biomass. We first characterized wastewater-grown algal samples and determined the optimal conditions (acid concentration, reaction temperature, and reaction time) for algal hydrolysis using dilute sulfuric acid. The optimal condition for algal hydrolysis (considering release of both protein and sugar) was 4% sulfuric acid (w/w) at 116 °C for 30 min. Under this condition, 66% of the total protein and 99% of the total carbohydrate were released into the algal hydrolysate. Neutralized algal hydrolysate was then tested as a reaction medium (replacing the pH buffer solution) for the enzymatic hydrolysis of alkaline treated anaerobically-digested fiber. Our results showed that net glucose yields from enzymatic hydrolyses containing undiluted algal hydrolysate were at least 65% higher than net glucose yields from control media (bovine serum albumin solution, citrate buffer or distilled water), It is likely that the increase in net glucose yield is due, in part, to the binding of hydrolyzed algal proteins to lignin. This binding protects cellulase from binding to lignin. This study demonstrates a potential approach of using wastewater-grown algae as a co-substrate to significantly enhance the enzymatic hydrolysis of lignocellulose materials.