GROWTH AND ENRICHMENT OF PENTACHLOROPHENOL-DEGRADING MICROORGANISMS IN THE NUTRISTAT, A SUBSTRATE CONCENTRATION-CONTROLLED CONTINUOUS-CULTURE

The nutristat, a substrate concentration-controlled continuous culture , was used to grow pentachlorophenol (PCP)-degrading microorganisms. T he PCP concentration control system consisted of on-line measurement o f the PCP concentration in the culture vessel with a tangential filter and a flowthrough spectrophotometer. With PCP concentrations between 45 and 77 muM, a stable situation was established in the nutristat, wi th an average dilution rate of 0.035 +/- 0.003 h-1. Compared with thos e of fed-batch cultures and chemostat cultures, the growth rates of mi croorganisms in the PCP nutristat were significantly higher, leading t o considerable time savings in the enrichment procedure. In addition, PCP accumulation to severe inhibitory levels in the culture is prevent ed because the set point determines the (maximum) PCP concentration in the culture. The use of the nutristat as a tool for the growth of bac teria that degrade toxic compounds is discussed.