To screen various commercial microbial products for effectiveness in enhancing biodegradation of weathered Alaskan crude oil, a series of laboratory tests were conducted of 10 different products. The products were tested by electrolytic respirometry, to measure oxygen uptake over time, and in shaker flask microcosms, to measure oil degradation and microbial growth. Results supported the decision to field test two of the products.

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Bench-scale biodegradability studies of the Alaskan weathered crude oil were undertaken as part of the bioremediation project for the shorelines of Prince William Sound Alaska, contaminated by the Exxon Valdez oil spill. The purpose of the studies was to evaluate the ability of the indigenous microbial consortium of the seawater and island beach areas to biodegrade the weathered crude oil's alkane hydrocarbon and polynuclear aromatic (PAH) constituents in batch-type respirometric reactors and shaker flask systems. Biodegradation studies used Inipol EAP22 and water-soluble nitrogen and phosphorus-containing solution (OECD) as the fertilizer nutrient source. In the respirometric studies, the unpolluted beach material in seawater was spiked with 1,000, 300, and 100 mg/L of weathered crude oil and with Inipol at 5 percent of oil weight or with OECD stock solution concentrates. The contents were brought up to 1,000 mL with seawter. Unpolluted beach material spiked with 10,000, 3,000, and 1,000 mg/L of weathered crude oil and with either Inipol at 5 percent of oil weight or with OECD inorganic salts in 1,000 mL of seawater were used in shaker flask microcosm studies. Temperature of incubation in both studies was 15° C, and culture systems were incubated in darkness. Cumulative oxygen uptake data, growth data, and gas chromatography/mass spectrometry analysis data demonstrate almost complete utilization of the alkane hydrocarbon constituents in the presence of Inipol fertilizer and OECD synthetic medium, and significant biodegradation of the PAH constituents after six weeks of incubation. Control experiments without Inipol or OECD nutrients demonstrated absence of biodegradative activity.

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