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Methanol-oxidizing bacteria may play an important role in the development and use of biological treatment systems for the removal of methanol from industrial effluents. Optimization of methanol degradation potential in such systems is contingent on availability of nutrients, such as nitrogen, in the most favorable form and concentration. To that end, this study examined the variation in growth, methanol degradation, and bacterial diversity of two mixed methylotrophic cultures that were provided nitrogen either as ammonium or nitrate and in three different concentrations. Methanol-degrading cultures were enriched from biofilms sampled at a pulp and paper mill and grown in liquid batch culture with methanol as the only carbon source and either ammonium or nitrate as the only added nitrogen source. Results indicate that growth and methanol removal of the mixed cultures increase directly with increased nitrogen, added in either form. However, methanol removal and bacterial diversity, as observed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) methods, were higher when using nitrate as the nitrogen source for enrichment and growth, rather than ammonium. Based on results described here, nitrate may potentially be a better nitrogen source when enriching or working with mixed methylotrophic cultures, and possibly more effective when used as a nutrient addition to biofilters.

A number of isolates ofPenicillium rubrum have been examined for their ability to produce the toxic metabolites Rubratoxins A and B. Some were found to produce relatively large quantities of Rubratoxin A, others to produce mainly Rubratoxin B and two strains, both isolated from samples of paper, were found not to produce any toxic metabolites under the cultural conditions used. A method for assaying Rubratoxin A in mixtures of the two toxins is described. The formal relationship of these toxins with other metabolites produced by related moulds is briefly discussed.