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Background  Taking into account its thermotolerance, high growth rate, and broad substrate spectrum,  Kluyveromyces marxianus  can be considered an ideal consolidated bioprocessing (CBP). A major obstacle to ethanol production using  K. marxianus  is the low production of lignocellulolytic enzymes, which reduces the cellulose hydrolysis and ethanol production. Thus, further improvement of enzyme expression and secretion is essential.    Results  To improve the expression of lignocellulolytic enzymes, the inulinase promoter and signal sequence from  K. marxianus  was optimized through mutagenesis. A T(-361)A mutation inside the promoter, a deletion of AT-rich region inside 5′UTR (UTR∆A), and a P10L substitution in the signal sequence increased the secretory expression of the feruloyl esterase Est1E by up to sixfold. T(-361)A and UTR∆A increased the mRNA expression, while the P10L substitution extended the hydrophobic core of signal sequence and promoted secretion of mature protein. P10L and T(-361)A mutations increased secretory expressions of other types of lignocellulolytic enzymes by up to threefold, including endo-1,4-β-glucanase RuCelA, endo-1,4-β-endoxylanase Xyn-CDBFV, and endo-1,4-β-mannanase MAN330. During the fed-batch fermentation of strains carrying optimized modules, the peak activities of RuCelA, Xyn-CDBFV, MAN330, and Est1E reached 24 U/mL, 25,600 U/mL, 10,200 U/mL, and 1220 U/mL, respectively. Importantly, higher yield of enzymes by optimized promoter and signal sequence were achieved in all tested carbon sources, including the major end products of lignocellulose saccharification and fermentation, with growth on xylose resulting in the highest production.    Conclusions  The engineered promoter and signal sequence presented increased secretory expressions of different lignocellulolytic enzymes in  K. marxianus  by means of various carbon resources. Activities of lignocellulolytic enzymes in fed-batch fermentation were the highest activities reported for  K. marxianus  so far. Our engineered modules are valuable in producing lignocellulolytic enzymes by  K. marxianus  and in constructing efficient CBP strains for cellulosic ethanol production.    Electronic supplementary material  The online version of this article (10.1186/s13068-018-1232-7) contains supplementary material, which is available to authorized users.

Improved secretory expression of lignocellulolytic enzymes in Kluyveromyces marxianus by promoter and signal sequence engineering