PRODUCTION OF FUEL ALCOHOL FROM HULL-LESS BARLEY BY VERY HIGH GRAVITYTECHNOLOGY

Very high gravity mashes (>30 g dissolved solids per 100 ml) were prep ared from an experimental hull-less barley (SB90354) and fermented wit h active dry yeast. A maximum ethanol concentration of 17.1% (v/v) was realized in fermented mash, and a total ethanol yield of 443 L per to nne of barley (dwb) was obtained. To prevent excess viscosity during m ashing, it was necessary to hydrolyze beta-glucan in ground barley usi ng crude preparations of beta-glucanase or Biocellulase. While both th ese preparations possessed an endoglucanase activity, no measurable ex oglucanase activity was detected. A typical mash prepared at a water-t o-grain ratio of 3:1 and without hydrolysis of beta-glucan had a visco sity of 2,480 BU, while the viscosities of the mashes prepared after h ydrolysis of beta-glucan with beta-glucanase or Biocellulase were 560 and 240 BU, respectively. Hydrolysis of beta-glucan not only reduced t he viscosity of the barley mash but also released water bound and trap ped by the beta-glucan gel. The free amino nitrogen (FAN) content of t he barley mashes was high when compared to wheat mashes, and about 80% of this FAN was taken up by yeast. In spite of the high FAN content o f the mash, an exogenously added nitrogen supplement stimulated yeast growth and fermentation.