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  • br Conclusions We can conclude that Arg is important but

    2019-10-08


    Conclusions We can conclude that Arg293 is important but not indispensable for MeGlcA recognition by EcXyn30A since the R293A variant still retains activity and preference 9184 for MeGlcA-substituted substrates. The substrate specificity of GH30_8 glucuronoxylanases is most probably determined by an overall topology of substrate binding site employing several 9184 and ensuring recognition of MeGlcA side chain linked to xylosyl residue accommodated in -2a subsite. Although a very slow side reaction, the observed capability of EcXyn30A and its R293A variant to catalyze glycosyl transfer reactions with linear xyloooligosaccharides, namely with Xyl5, leading to products of DP higher than 10, calls our attention to a synthetic potential of bacterial GH30 glucuronoxylanases which would be worth of investigation.
    Declarations of interest
    Acknowledgements Funding: This work was supported by the Slovak Research and Development Agency under the contract No. APVV-0602-12, and by Scientific Grant Agency under the contract Nos. 2/0016/18 and 2/0092/17. This work was also supported by the Research and Development Operation Programme funded by the European Regional Development Fund (ITMS 26220120054).
    Introduction Lipases (triacylglycerol acyl hydrolases, E.C. 3.1.1.3) constitute an important class of enzymes that catalyze the hydrolysis of triacylglycerol ester bonds at oil/water interface (Manoel et al., 2015). Microbial lipases stand out in the current industrial scenario due to its broad application spectrum, which may be related to their diverse functions. In addition to hydrolysis of long-chain triglycerides, these enzymes can catalyze the reverse reaction in organic media, performing esterification of fatty acids and glycerol into triglycerides, as well as acting on transesterification, and alcoholysis reactions, among others (Tan et al., 2015, Kumar et al., 2016). Lipases are considered an environmentally friend alternative for many industrial processes, contributing to reduce the amount of largely employed chemicals. In detergents, they can be used as biodegradable and non-toxics additives, resulting in harmless residues (Sharma et al., 2017). In the production and refinement of oleochemicals, lipases are efficiently applied to release fatty acids and glycerol from lipids (Ibrahim et al., 2008). In the food industry, lipases are applied to enhance dairy flavor and in the processing of meat, vegetables, fruits and beer; in addition, they can also be used to reduce calories of lipids by fatty acids transesterification (Houde et al., 2004, Aravindan et al., 2007). In pharmaceutical and cosmetic industries, lipases are used to obtain mono-, di- and triglycerides that may act as colorants, fragrances, and sunscreen or makeup additives. Lipases may be also applied on leather manufacture for lipids removal (Gandhi, 1997). Filamentous fungi are excellent enzymes producers under submerged and solid-state cultivation conditions. Lipases from Penicillium species show high potential in fermentation platforms: lipase from Penicillium simplicissimum was produced with triolein as carbon source, and the enzyme purified showed molecular weight of 56 kDa and stability in the pH from 5 to 7 and at 50 °C (Sztajer et al., 1992). In other studies, lipase from P. simplicissimum was obtained after solid state cultivation using mixed substrate and low-cost nitrogen sources (Gutarra et al., 2007, Vargas et al., 2008) and the enzyme was purified and immobilized using hydrophobic supports under interfacial activation conditions (Cunha et al., 2009). Penicillium wortmanii was screened as the best lipase producer using 5% (w v−1) olive oil as the carbon source; and the crude lipase presented optimum activity at pH 7.0 and 45 °C; besides the enzyme was highly stable at 40 and 45 °C and retained 55% of activity at 50 °C (Costa and Peralta, 1999). Lipase from Penicillium restrictum was obtained in solid waste from the babassu oil industry supplemented with peptone, olive oil or starch. Lipase activity was very sensitive to the type and level of supplementation, and it was decreased by increasing protease level and pH of the media (Gombert et al., 1999). An economic analysis of lipase production by P. restrictum in both submerged and solid state fermentations performed at 100 m3 lipase/year production scale, showed that the submerged process is economically unfeasible, with the unitary product cost 68% higher than the product selling price, however the solid-state fermentation is very attractive from an economic point of view with the product cost 47% lower than the selling price, presenting 1.5 years payback time, 68% investment return of and 62% internal return rate in a 5-year-project life (Castilho et al., 2000).