Collaborators from the Tokyo University of Agriculture and Technology (TUAT) developed a two-step method that efficiently breaks down carbohydrates into monomers, single sugar components that are related with producing green fuel. The researchers published their work in the journal Industrial & Engineering Chemical Research.
Saccharification is the breakdown process where monosaccharides or single sugar components are produced. These simple sugars can be fermented into biobutanol or bioethanol which can be used as fuel.
"For a long time, considerable attention has been focused on the utilization of homogenous acids and enzymes for saccharification," said Eika W. Qian, paper author and professor in the Graduate School of Bio-Applications and Systems Engineering at the Tokyo University of Agriculture and Technology in Japan. "Enzymatic saccharification is seen to be a reasonable prospect since it offers the potential for higher yields, lower energy costs, and it's more environmentally friendly."
The breakdown of carbohydrates in biomass such as rice straw through enzymes could actually be stopped. Starch, hemicellulose, and cellulose comprise rice straw. The cell wall structure and surface area are some of the properties that do not allow enzymes to break down cellulose or hemicellulose. These require an expensive pre-treatment so they can be sensitive to the approach of the enzymes.
The use of solid acid catalysts is the solution to the concerns related with the enzymes. These acids do not take part in the reaction as they can be reused and recovered after saccharification.
The non-uniformity of carbohydrates increases the difficulty in doing the process even if acids replace the enzymes.
"Hemicellulose and starch degrade at 180 degrees Celsius and below, and if the resulting components are heated further, the sugars produced discompose and are converted to other byproducts. On the other hand, degradation of cellulose only happens at temperatures of 200 degrees Celsius and above," according to Eureka Alert.
The researchers were able to maximize the resulting yield of sugar from rice straw by developing a two-step process. "
"The first step requires a gentle solid acid at low temperatures (150 degrees Celsius and below), while the second step consists of harsher conditions, with a stronger solid acid and higher temperatures (210 degrees Celsius and above)," as reported in Eureka Alert.
The two-step process was not only effective, an additional 30 percent more sugars were produced.
"We are now looking for a partner to evaluate the feasibility of our two-step saccharification process in rice straw and other various materials such as wheat straw and corn stoke etc. in a pilot unit," Qian said. "Our ultimate goal is to commercialize our process to manufacture monosaccharides from this type of material in the future."
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