Joseph J. Gauthier

Conversion of cyanide to formate and ammonia by a pseudomonad obtained from industrial wastewater

SummaryA cyanide-degrading pseudomonad was isolated by selective enrichment in a chemostat inoculated with coke-plant activated sludge and maintained at a dilution rate of 0.042/h for 60 days with a feed of 10 mg/l cyanide. The isolate, a facultative methylotroph capable of growth on methanol and methylamine, degraded cyanide to formate and ammonia; it could utilize the released ammonia as a nitrogen source but did not further metabolize formate under the experimental conditions employed. Both cyanide-degrading enzyme activity and respiratory resistance to cyanide were inducible and were enhanced by repeated exposure to the compound. Cell-free extracts stoichiometrically converted cyanide to formate and ammonia in a reaction that did not require oxygen. Enzyme activity, lost upon dialysis, was restored by less than equimolar ratios of NAD(P)H or ascorbate to cyanide, indicating that the reductants did not function directly as co-enzymes.

Biodegradabilities and Microbial Activities During Composting of Municipal Solid Waste In Bench-Scale Reactors

In the design of large scale, in-vessel systems, the biodegradability of the waste, the optimal nutritional conditions, and the length of time required to complete the high-rate phase are important. Because composting is a microbial process, the overall levels and activities of microorganisms influence the rate and extent of degradation. In this study, bench-scale reactors were used to determine the biodegradability of municipal solid waste, primarily office trash, and the effects of nutrient supplementation on biodegradability during six weeks of composting. Supplementation with nitrogen, phosphorus, vitamins, and trace minerals did not increase the biodegradability of the waste. Although the levels of specific microbial subpopulations varied, total numbers of microorganisms did not change significantly.

Microbial activities during composting of pulp and paper-mill primary solids

In this study, bench-scale aerobic reactors were used to monitor microbial activities and determine the degradability of pulp and paper-mill primary solids. Over the 43-day composting period, the level of microorganisms detected increased four-fold. However, based on amounts of CO2 produced, the increase expected was 19-fold, suggesting lysis of some cells in the population. The composition of the microbial population, determined through species identification by the BIOLOG® method, and by spot plating, changed throughout the composting process with Cellulomonas spp. not appearing until day 22. Chemical analyses suggested a fall of 33% in the cellulose content, but no other statistically significant chemical changes were observed.

Putative anaerobic activity in aerated composts

It has been suggested that anaerobic microenvironments develop in aerobic composts, regardless of the aeration system used, and that anaerobic activity is responsible for odor generation and nitrogen losses. This study was designed to measure levels of microorganisms capable of anaerobic growth in two aerated composts: municipal solid waste, a relatively nutrient-rich compost, and pulp and paper-mill solid waste, which is relatively nutrient-poor. Anaerobic microorganisms were isolated from both composts at mesophilic and thermophilic temperatures. The majority of the anaerobic mesophiles were facultative anaerobes, whereas facultative, anaerobic thermophiles varied from 0 to 100%. Serially-diluted samples were spot-plated onto various media to preserve microbial consortia. Levels of aerobic and anaerobic exoenzyme production on spot-plates were similar on cell-wall, starch, and casein media. Although microbial levels on spread plates indicate that aerobes are present in much higher numbers than anaerobes (in 47 of 56 subsamples, 90% of the population were aerobes), microbial growth levels and exoenzyme production on spot-plates indicate that anaerobes may be responsible for a large portion (greater than or equal to 72%) of the metabolic activity in anaerobic microenvironments of aerobic composts.

Biodegradabilities and Microbial Activities During Composting of Oxidation Ditch Sludge

Best design of a compost system is dependent on knowing the degradability of the waste. Although many bulking agents used to adjust moisture and porosity consist of organic matter, it is usually assumed they contribute only a small proportion of the total degradable material in a compost mix. As the microorganisms degrade the organic compounds during composting, it is generally presumed that they grow, and increase in biomass and numbers. In this study, bench-scale compost reactors were used to determine the relative contributions of sewage sludge and the bulking agent (pine sawdust) to the biodegradability of a compost mix. Although the overall level of microorganisms did not change markedly during composting, subpopulations able to degrade selected macromolecules were present at varying levels. Populations capable of degrading bacterial cell walls and thereby of contributing to recycle of inorganic nutrients through biomass turnover were present throughout the composting period.