An extracellular lipase, LipA, extracted from Acinetobacter sp. RAG-1 grown on hexadecane was purified and properties of the enzyme investigated. The enzyme is released into the growth medium during the transition to stationary phase. The lipase was harvested from cells grown to stationary phase, and purified with 22% yield and > 10-fold purification. The protein demonstrates little affinity for anion exchange resins, with contaminating proteins removed by passing crude supernatants over a Mono Q column. The lipase was bound to a butyl Sepharose column and eluted in a Triton X-100 gradient. The molecular mass (33 kDa) was determined employing SDS/PAGE. LipA was found to be stable at pH 5.8-9.0, with optimal activity at 9.0. The lipase remained active at temperatures up to 70°C, with maximal activity observed at 55°C. LipA is active against a wide range of fatty acid esters of p-nitrophenyl, but preferentially attacks medium length acyl chains (C 6 , C 8 , but shows no loss in activity after incubation with other metals or inhibitors examined in this study. The protein retains more than 75% of its initial activity after exposure to organic solvents, but is rapidly deactivated by pyridine. RAG-1 lipase offers potential for use as a biocatalyst.
An active sulfate-reducing consortium that degrades 2-methylnaphthalene (2-MNAP) at rates of up to 25 M day ؊1 was established. Degradation was inhibited in the presence of molybdate and ceased in the absence of sulfate. As much as 87% of 2-[ 14 C]MNAP was mineralized to 14 CO 2 . 2-Naphthoic acid (2-NA) was detected as a metabolite, and incubation with either deuterated 2-MNAP or [13 C]bicarbonate indicates that 2-NA is the result of oxidation of the methyl group. Also detected were carboxylated 2-MNAPs, suggesting the presence of an alternative pathway for 2-MNAP degradation.
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