Ethanol production from starchy materials by conventional
fermentation requires saccharification with amylolytic enzymes
and subsequent fermentation using the yeast Saccharomyces cerevisiae,
because this yeast cannot utilize starchy materials. The
two-step process results in high production costs and low
productivity of ethanol. Many reports have been published on the
development of S. cerevisiae strains capable of secreting amylolytic
enzymes [2]. Although yeast strains capable of utilizing
starch have been developed, their ethanol-producing ability
remains unsatisfactory. Recently, yeast strains displaying various
proteins on their cell surface have been developed using genetic
engineering [3]. Laboratory yeast strains displaying Rhizopus
oryzae glucoamylase (EC 3.2.1.3) [4], which cleaves glucose from
a-1,4-linked and a-1,6-linked polysaccharides, have produced
ethanol directly from soluble and cooked corn starch [5,6].