Fig. 1

Diagram of gene cassettes and vector used for cellulase expression in L. starkeyi. a Cellulase gene expression cassette; b the base vector, in which the star denotes where genes of interest are cloned into. Bla, beta-lactamase gene for ampicillin resistance; PGK1 trm, 3-phosphoglycerate kinase gene’s terminator; pPYK, promoter of L. starkeyi pyk (pyruvate kinase gene); spAMY, signal peptide of L. starkeyi amylase; spDEX1, signal peptide of L. starkeyi dextranase 1; spDEX2, signal peptide of L. starkeyi dextranase 2; spPRO, signal peptide of Y. lipolytica protease; TDH3 pro, glyceraldehyde-3-phosphate dehydrogenase gene’s promoter; tGAL1, terminator of L. starkeyi gal1 (galactokinase 1 gene); 2µ, S. cerevisiae 2-micron origin of replication. Gene, cellulase gene without native signal peptide. Size of various signal peptides is described in Table 2, while the size of chimeric CBH I and EG II is 500 and 397 in amino acid residues, respectively; the size of fusion genes that encode signal peptide-cellulase can be deduced accordingly