Abstract: Screening of new microorganism being able to produce efficiently
flocculants was carried out. A new model for screening efficient
flocculant-producing strains was designed and tested. The results showed that
this model for screening efficient flocculant-producing strains is very
reliable and can greatly shorten the screening period. 13 flocculant-producing
strains were isolated from activated sludge by conventional method. A strain,
designated as HHE6, produced the bioflocculant with the turbidity removal 98%
for kaolin suspension. Six of 13 strains selected as the original strains were
treated with NTG as mutagen, and five mutant strains (HHE-P7, HHE-A8, HHE-P21,
HHE-P24, HHE-A26) with high flocculation efficiency was obtained by selection,
which exhibited the flocculation rate for kaolin suspension above 90%. Strains
HHE6, HHE-P7, and HHE-P24 were classified as Penicillium purpurogenum, HHE-P21
as Penicillium cyclopium, HHE-A26 as Aspergillus versicolor and HHE-A8 as
Aspergillus fumigatus, and it is hitherto unreported for
biofloccutant-producing strains of Penicillium. The growth of the six strains
(HHE6, HHE-P7, HHE-A8, HHE-P21, HHE-P24, HHE-A26) had similar curves, i.e.
firstly increasing rapidly, keeping relatively constant then and finally
decreasing gradually with cultivation time. The production of bioflocculants by
strains showed the similar pattern to strain growth.
