Abstract:

【Objective】 The objective of this study was to reveal the characteristics of a strain (M25-22) of Penicillium sp. with the capacity of heterotrophic ammonium oxidation isolated from chicken feces compost, and to provide scientific references for its application in aerobic composting. 【Method】 Media with ammonium salt as the sole nitrogen source was used to determine the heterotrophic ammonium oxidation activity of the strain. Some environmental factors, such as compositions of carbon and nitrogen sources, concentrations of sucrose and ammonium nitrogen, initial pH and culture temperature, were adjusted to gain better insight into the effects of them on ammonium oxidation by the strain. 【Result】 In media containing (NH4)2SO4 at a concentration of 0.5 g/100 mL, mycelium weight and utilization ratio of ammonium nitrogen increased markedly during the first 5 days; nitrate concentration increased markedly from the 3rd to 5th day, and remained constant thereafter; nitrite concentration remained at a low level. The strain showed an ability to oxidize ammonium nitrogen growing in media containing glucose, sucrose, starch or cellulose as the sole carbon source, and to oxidize the negative trivalent nitrogen of ammonium sulfate, peptone, acetamide, urea or L-aspartate. Slowly available carbon or nitrogen sources, such as starch, cellulose and peptone, were beneficial to ammonium oxidation by the strain. In media containing sucrose as the sole carbon source and ammonium sulfate as the sole nitrogen source, nitrate formation was the most pronounced with sucrose present at a concentration of 12 g•L-1 and ammonium nitrogen present at a concentration of 2.438 mg•mL-1, at the initial pH level of 7.5 and at 30℃. 【Conclusion】 There is an inorganic nitrogen nitrification pathway of bacteria in the strain. Ammonium oxidation by the strain is involved in secondary metabolism. The strain is capable of oxidizing a variety of reduced nitrogen with different carbon sources, and has an enormous capacity for ammonium oxidation at high concentrations of organic substance and ammonium nitrogen. It is indicated that the strain has an expansive application prospect in aerobic composting of solid waste.

Key words: aerobic composting, heterotrophic ammonium oxidation, Penicillium sp., secondary metabolism