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Oxidation of hydrogen sulfide by flocculated Thiobaccillus denitrificans in a continuous culture
Author(s) -
Ongcharit Chawan,
Sublette Kerry L.,
Shah Y. T.
Publication year - 1991
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260370602
Subject(s) - heterotroph , autotroph , paracoccus denitrificans , biomass (ecology) , chemistry , bioreactor , fermentation , sulfate reducing bacteria , thiobacillus , industrial fermentation , effluent , hydraulic retention time , environmental chemistry , bacteria , food science , sulfate , biology , biochemistry , environmental engineering , ecology , organic chemistry , genetics , sulfur , enzyme , engineering
In a continuous fermentation, significant advantages may be gained by immobilization of microbial cells. Immobilization allows cells to be retained in the fermenter or to be readily recovered and recycled. Therefore, the hydraulic retention time and the biomass retention time are decoupled. A novel cell immobilization has been developed for the immobilization of autotrophic bacteria by coculture with floc‐forming heterotrophic bacteria with growth of the latter limited by the availability of organic carbon. The result is an immobilization matrix which grows along with the immobilized autotroph. We have previously demonstrated the utility of this approach by immobilizing the chemoautotroph Thiobacillus denitrificans in macroscopic floc by coculture with floc‐forming heterotrophs from an activated sludge treatment facility. Floc with excellent settling characteristics were produced. These floc have now been used to remove H 2 S from a gas stream bubbled through continuous cultures. The stoichiometry and kinetics of H 2 S oxidation by immobilized T. denitrificans were comparable to that reported previously for free‐cell cultures. Oxygen uptake measurements indicated the growth of both T. denitrificans and the heterotrophs although the medium contained no added organic carbon. Continuous cultures with total biomass recycle were maintained for up to four months indicating the long‐term stability of the commensal relationship between the immobilized autotroph and the heterotrophs which composed the immobilization matrix. It was observed that at any given H 2 S loading the biomass concentration reached a maximum and leveled out. The ultimate biomass concentration was dependent upon the H 2 S feed rate.