Thermoalkaliphilic laccase treatment for enhanced production of high-value benzaldehyde chemicals from lignin

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Enzymatic conversion of lignin into high-value chemicals is a key step in sustainable and eco-friendly development of lignin valorization strategies. In the present study, a novel thermoalkaliphilic laccase, CtLac, from <I>Caldalkalibacillus thermarum</I> strain TA2.A1 was tested for the depolymerization of lignin and the production of value-added chemicals, using three different lignocellulosic biomass, organosolv lignin (OSL), and Kraft lignin. Seven valuable lignin monomers were identified from the CtLac-treated samples using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Remarkably, increases of 22.0%, 65.6%, and 27.3% of <I>p</I>-hydroxybenzaldehyde and increases of 111.1%, 93.5%, and 238.1% of vanillin were observed from rice straw, corn stover, and reed, respectively. Comparative analysis of lignin monomers released from rice straw, using <I>Trametes versicolor</I> laccase (TvL) and CtLac indicated efficient depolymerization of lignin by CtLac. CtLac treatment resulted in 2.3 fold and 5.6 fold, and 1.9 fold and 2.8 fold higher amounts of <I>p</I>-hydroxybenzaldehyde and vanillin from OSL and Kraft lignin, respectively, compared to CtLac-treated rice straw samples after 12 h reaction. OSL was the best substrate for the production of benzaldehyde chemicals using CtLac treatment. The results demonstrated potential application of bacterial laccase CtLac for valorization of biomass lignin into high-value benzaldehyde chemicals under thermoalkaliphilic conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel thermoalkaliphilic laccase CtLac, was investigated for lignin depolymerization. </LI> <LI> Lignin monomers released after CtLac treatment were analyzed using HPLC-MS/MS analysis. </LI> <LI> High-value benzaldehyde chemicals <I>p</I>-hydroxylbenzaldehyde and vanillin were released from lignin after CtLac treatment. </LI> <LI> CtLac treated Organosolv lignin released highest amount of benzaldehyde chemicals. </LI> <LI> CtLac favored depolymerization of lignin under thermoalkaliphilic conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>