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Pink yeasts identified as Rhodotorula glutinis var. glutinis, R. minuta var. minuta, and R. rubra produce polygalacturonases which cause a slow softening of olive tissue. Both pectin methyl esterase and polygalacturonase are produced when cultures are grown in appropriate media. Crude, cell-free dialyzed enzyme preparations measured viscosimetrically exhibited optimal activity on sodium polygalacturonate at pH 6.0 and 40 C, and were active in the range of pH 4.0 to 9.0 and 10 to 50 C. Cultures grown in sterilized olives and brine atpH 4.0 with sterile glucose added aseptically caused a slow softening of tissue as measured with a Christel texturometer. Similar results were obtained when crude, cell-free enzyme preparations were added to olives in buffer solution at pH 6.0 with Merthiolate. Commercial control of these yeasts is easy if anaerobic conditions can be provided. Otherwise, the industry has to resort to manual removal of the film from the brine surface, either by skimming or by flagellation.

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Conventional treatment of a mixed-metal wastewater consists ofhydroxide precipitation of the metals at an alkaline pH, followed by removal of the resulting solids by simple sedimentation and sometimes filtration. Hexavalent chromium removal is preceded by reduction to the less soluble trivalent chromium. Sulfur compounds (sodium sulfite, etc.) are commonly used reducing agents with the reaction carried out at pH 2 to 3. Treatment complexity results from the need to maintain separate acidic and alkaline cesses. Efficient alkaline reduction of hexavalent c romium would consolidate these two processes, simplify the treatment of mixed-metals wastewater, and reduce acid and base usage. Bennet [I] and Watson [Z] stated that an acidic pH (lessof Technology in 1963. He also received B.S. and M.S. degrees in Chemical Engineering from I.I.T. in 1957 and 1959. His major areas of interest include process instrumentation and control with an emphasis on digital computer applications. Environmental M r w r (Vol. 3, No. 1)

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