Effect of thermoplastic extrusion of maize on the efficiency of bioethanol production of high concentred worts fermented with Zymomonas mobilis

摘要

The growing demand for efficient processes and fermentation technologies for fuel ethanol production have been the driving force for the implementation of thermoplastic extrusion. This technology allows the quick gelatinization of starch. The aim of this research was to compare the use of extruded maize meals with dried ground maize in terms of characteristics of worts obtained after conventional liquefaction and saccharification. The materials have shown a 17.54% and 7.652% WSI for the extruded and ground maize, respectively. The notorious difference is attributed to structural changes due the mechanical and thermal stress produced during extrusion. Worts were evaluated in terms of Brix content (12 and 20 °P), pH and FAN content. Results indicated that worts contained a similar initial pH (5.51 ±0.09) and FAN content. The rate of consumption of FAN compounds present in worts adjusted to 12°P it was not significant different among treatments (p>0.05).However, the thermoplastic extruded maize increased approximately 15.45% the rate of FAN consumption after 8h. The initial fermentable sugar content of worts adjusted two 20°P was 2.14% higher in the extruded maize wort compared to the regular ground maize. Zymomonas mobilis was capable of fermenting with good efficiency worts adjusted to 20°P. The 20°P worts produced from extruded meals had approximately 21.2% less fermentable sugars after 8 h fermentation compared to counterparts produced from regular maize meal. This research demonstrated that Zymomonas mobilis was capable of fermenting 20°P worts and that the bacterium was more efficient fermenting liquefied and saccharified extruded meals.