AUTHOR=Shi Zelu , Han Chao , Zhang Xiujun , Tian Li , Wang Lushan 

TITLE=Novel Synergistic Mechanism for Lignocellulose Degradation by a Thermophilic Filamentous Fungus and a Thermophilic Actinobacterium Based on Functional Proteomics

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.539438

DOI=10.3389/fmicb.2020.539438

ISSN=1664-302X

ABSTRACT=<p>Effective artificial microbial consortia containing microorganisms with desired biological functions have the potential to optimize the lignocellulose-based bioindustry. <italic>Thermobifida fusca</italic> was a dominant actinobacterium in high-temperature corn stalk composts, but it was unable to grow alone in corn stalk solid medium. Interestingly, <italic>T. fusca</italic> showed good growth and secreted enzymes when cocultured with <italic>Thermomyces lanuginosus</italic>. <italic>T. lanuginosus</italic> grew firstly during the initial stage, whereas <italic>T. fusca</italic> dominated the system subsequently during cocultivation. The secretome indicated that <italic>T. lanuginosus</italic> mainly degraded xylan by expressing a GH11 xylanase (g4601.t1, GenBank AAB94633.1; with relative secretion of 4.95 ± 0.65%). <italic>T. fusca</italic> was induced by xylan mainly to secrete a xylanase from GH11 family (W8GGR4, GenBank AHK22788.1; with relative secretion of 8.71 ± 3.83%) which could rapidly degrade xylan to xylo-oligosaccharide (XOS) and xylose within 2 min, while high concentrations (&gt;0.5%, w/v) of XOS or xylose suppressed the growth of <italic>T. fusca</italic>; which may be the reason why <italic>T. fusca</italic> unable to grow alone in corn stalk solid medium. However, <italic>T. lanuginosus</italic> could utilize the XOS and xylose produced by xylanases secreted by <italic>T. fusca</italic>. During the synergistic degradation of lignocellulose by <italic>T. lanuginosus</italic> and <italic>T. fusca</italic>, xylan was rapidly consumed by <italic>T. lanuginosus</italic>, the residual cellulose could specifically induced <italic>T. fusca</italic> to express a GH10 xylanase with a CBM2 domain (Q47KR6, GenBank AAZ56956.1; with relative secretion of 5.03 ± 1.33%) and 6 cellulases (2 exocellulases and 4 endocellulases). Moreover, <italic>T. lanuginosus</italic> increased the secretion of cellulases from <italic>T. fusca</italic> by 19–25%. The order of <italic>T. lanuginosus</italic> and <italic>T. fusca</italic> was consistent with the multilayered structures of lignocellulose and could be regulated by different concentrations of XOS and xylose. The novel synergism of <italic>T. lanuginosus</italic> and <italic>T. fusca</italic> gave a new sight for revealing more synergetic relationships in natural environments and exploring efficient microbial inoculants and enzyme cocktails for lignocellulose degradation.</p>