Liquefaction of Starch by a Single-screw Extruder and Post-extrusion Static-mixer Reactor

摘要

The production of ethanol has increased rapidly during the past few years, especially since enactment of the 1990 Clean Air Act. Production costs, however, are high, requiring improved conversion technologies. The gelatinization of starch with conventional jet cookers requires a minimum moisture content of 65% by weight. An alternative to jet cookers is extrusion, which requires significantly less moisture to gelatinize starch. Starch gelatinization and liquefaction was achieved using single-screw extrusion and a post-extrusion static-mixer reactor. The effects of moisture content, reactor temperature, reactor length, and enzyme concentration on liquefaction were evaluated using response surface methodology. The use of a static-mixer reactor tube improved mixing of the gelatinized slurry and increased residence times, resulting in increased starch degradation and reduced viscosity. Comparison of costs for extrusion and conventional technology indicates extrusion has potential as a cost-effective alternative.