| Summary: | 碩士 === 大葉工學院 === 食品工程研究所 === 84 === Biosurfactants is a term that mainly refers to surface
active molecules that are produced by a variety of
microorganisms. As with most surface active materials, they have
a hydrophilic and a hydrophobic portion. In general the
advantages of these biomolecules over synthetic surfactants are
their low-toxicity, high-biodegradability and the easy to use
cheap, renewable substrate for commercial production. The
increasing interest in the potential application of microbial
surface active compounds is based on the ecological
compatibility concern in biotechnology development. This study
emplays a semi-continuous culture system which combines a two-
stage process with the immobilization of resting cells for
lipopeptide biosurfactant formation in Bacillus subtilis(ATCC
21332). Results appeared a decrease of the surface tension to 30
dyne/cm in the culture broth at 8hr under two-stage culture,
which led to shorter process and higher productivity. A chitosan
prepared by deacetylation of chitinwas chosen as the carrier for
cell immobilization. Various types of chitosan beads were
prepared through cross-linkage and functional groups
modification chemically to obtain better resistant and absorbent
capacity. The ultrastruction and the pore size distribation of
the chitosan beads from different preparation were observed
under SEM from different preparation. High loading of 8.7×107
cells/ml-bead was achieved in carboxyl modification of CCB. The
maximum production of surfactin from broth quantified by HPLC to
reach 750mg/L in two-stage culture of B. subtilis. This paper
deals with the application of a novel semi-continuous cultural
system combined with cell immobilization also to simplify
separation process by foam recovery. A very active biosurfactant
which can reduce the surface tension to 23 dyne/cm from foam
collection liquid, the lowest value have ever been appeared in
literature, it exhibits the excellent technical creativity and
composite applications regarding industrial considerations.Key
word: Bacillus subtilis, biosurfactant, surfactin, cell
immobiliza-tion, semi-continuous cultural system, SEM, HPLC.
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