초록
<P>Lignin conversion to value-added products is one of the most attractive challenges to develop a complete system for lignocellulosic biomass utilization. The objective of this study was <I>cis</I>,<I>cis</I>-muconic acid (ccMA) production from lignin, in particular, without sugar. Here, two bacterial strains were developed that can synthesize ccMA from lignin without using glucose. One is applicable to softwood lignin (mostly guaiacyl-lignin), and the other is applicable to hardwood lignin (mostly syringyl- and guaiacyl-lignins). The engineered <I>Pseudomonas putida</I> KT2440-based strain produced ccMA from a mixture of vanillic acid (a guaiacyl-lignin model) and 4-hydroxybenzoic acid (a <I>p</I>-hydroxyphenyl-lignin model) with ∼20% yield (mol/mol) without supplement of glucose. The dissolved oxygen concentration of 5–10% was effective to produce ccMA with a higher yield. The <I>Sphingobium</I> sp. SYK-6-based strain produced ccMA from vanillic acid with ∼45% yield (mol/mol) while growing on syringic acid (a syringyl-lignin model). These ccMA-producing strains can synthesize ccMA from lignin extracts of Japanese cedar and birch without using glucose.</P><P>A platform chemical for polymer synthesis, <I>cis</I>,<I>cis</I>-muconic acid, is producible from only lignin via two types of sugar-free biocatalytic processes.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ascecg/2018/ascecg.2018.6.issue-1/acssuschemeng.7b03597/production/images/medium/sc-2017-035979_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/sc7b03597'>ACS Electronic Supporting Info</A></P>