Solid-state fermentation production and characterization of an alkaline lipase from a newly isolated <i>Burkholderia gladioli</i> strain

The newly isolated <i>Burkholderia gladioli</i> BRM58833 strain was shown to secrete an alkaline lipase highly active and stable in organic solvents. Lipase production was optimized through the cultivation of the strain by solid-state fermentation in wheat bran. The lipase extraction conditions were also optimized. The low-cost extract obtained has shown a high hydrolytic activity of 1096.7 ± 39.3 U·gds⁻¹ (units per gram of dry solids) against <i>p</i>NPP and 374.2 ± 20.4 U·gds⁻¹ against triolein. Proteomic analysis revealed the optimized extract is composed of two esterases and three true lipases, showing a preference for long-chain substrates. The highest activity was obtained at 50 °C and pH 9. However, the extract maintained more than 50% of its maximum activity between pH 8.0 and 10.0 and throughout the whole temperature range evaluated (32–70 °C). The enzymes were inhibited by SDS, EDTA, ZnSO₄ and FeCl₃ and activated by FeSO₄, MgCl₂ and BaCl₂. The lipases conserved their activity when incubated in solvents as acetonitrile, diethyl ether, <i>n</i>-heptane <i>n</i>-hexane, toluene, methanol and <i>t</i>-butanol. The resistance of these lipases to solvents and expressive thermostability when compared to other lipases, reveal their potential both in hydrolysis reactions and in synthesis of esters.