Cellulose to glucose

19 August 2015 - Catalysis

cellulose to glucose Katz 2015.PNG Anh The To et al. of the Alexander Katz group at Berkeley report on a faster way to hydrolyze crystalline cellulose to glucose. (DOI) This process is of interest to biofuels and the synthesis of chemicals from biological sources. Synthetic catalysts have an efficiency of 20% and for carbon catalysts the efficiency drops to 4%. The improved method is bioinspired. As enzymes have weak-acid sites for the activation of the glycosidic bonds so a carbon source is fitted with those weak-acid sites as well. Result: 70% yield of which 96% glucose.

The recipe: MSC-30 is a mesoporous carbon (more precise petroleum coke activated with molten
potassium hydroxide). This material was treated with sodium hypochlorite in water (RT, several hours). The pH was brought back from 12 to 5 by HCl treatment. It leaves surface-bound carboxylic acid groups as well as lactones and phenols, all weak acids.

The adsorption of cellulose on the carbon particles was tested by immersing them in a HCl solution of cellulose. Does it come as a surprise that compared to untreated carbon, the adsorption affinity for cellulose of the treated carbon is much reduced? In a real live hydrolysis reaction 1.5 mg of cellulose in 1 mL of water was treated with 20 mg of the carbon compound (that much?) at 150°C for 24 hours. The carbon varieties best equipped for adsorbing cellulose were now the worst performers. Top results were obtained for hypochlorite treated carbon at pH 5.

Nevertheless it seems a lot of work to hydrolyse cellulose this way. The efficiency of enzymatic hydrolysis compared to this work was not discussed. This blog attempted to get some data from the literature but although a mountain of articles have been written on the topic the simple question of crystalline cellulose + cellulase = ? conversion @temperature and @hours proved to be an impossible one to answer.