Different matrices viz. agar. alginate and polyacrylamide were examined for
the immobilization of whole cells of Ralstonia pickettii. The enzyme activ
ity of whole cells immobilized in agar beads was very low. Alginate beads h
ad the inherent disadvantage of dissolving in phosphate based media and eve
n glutaraldehyde treatment did not have any significant effect. A Tris-HCl
system was found to be the best for alginate based immobilization of whole
cells from R. pickettii and 4% alginate beads gave an optimal lipase activi
ty of 14 U/ml per min. When different concentrations of polyacrylamide were
tried for immobilization of R. pickettii whole cells, 15% polyacrylamide b
locks showed a retention activity of 66% (25 U/ml per min) when compared to
that of the free cells (40 U/ml per min). Bis-acrylamide concentration of
0.15 g/10 ml of buffer was ideal and the optimum whole cell concentration f
or polyacrylamide immobilization was 2.0 g/l of saline. Optimal immobilized
whole cell concentration (polyacrylamide blocks) for lipase production was
20% and polyacrylamide blocks were reused three times effectively for lipa
se production. Of the three matrices examined for the immobilization of who
le cells from R. pickettii polyacrylamide gave the best performance. (C) 20
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