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In order to improve the stability of endoglucanase under thermal and acidic conditions, the endoglucanase gene was fused to the N-terminus of the Saccharomyces cerevisiae pir gene, encoding the cell wall protein PIR. The fusion gene was transformed into Pichia pastoris GS115 for expression. A resulting strain with high expression and high activity was identified by examining resistance to Geneticin 418, Congo red staining, and quantitative analysis of enzyme activity. SDS-PAGE analysis revealed that the endoglucanase was successfully displayed on the yeast cell surface. The displayed endoglucanase (DEG) showed maximum activity towards sodium carboxyl methyl cellulose at approximately 275 IU/g cell dry weight. DEG exhibited greater than 60% residual activity in the pH range 2.5-8.5, higher than free endoglucanase (FEG), which had 40% residual activity at the same pH range. The highest tolerated temperature for DEG was 70°C, much higher than that of FEG, which was approximately 50°C. Moreover, DEG showed 91.1% activity at 65°C for 120 min, while FEG only kept 77.8% residual activity over the same period. The half-life of DEG was 270 min at 65°C, compared with only 150 min for FEG. DEG could be used repeatedly at least three times. These results suggest that the DEG has broad applications as a yeast whole-cell biocatalyst, due to its novel properties of high catalytic efficiency, acid-thermal stabilities, and reusability.

DNA barcoding is a supplementary tool in plant systematics that is extensively used to resolve species-level controversies. This study assesses the significance of using two DNA barcoding loci (e.g., psbA-trnH and trnC-petN) in distinguishing 33 plant samples of the genus Syringa. Results showed that the average genetic distance K2P of psbA-trnH DNA marker was 0.0521, which is much higher than that of trnC-petN, which is 0.0171. A neighbor-joining phylogenetic tree based on psbA-trnH and trnC-petN indicated that the identification rate of psbA-trnH and trnC-petN alone were 75% and 62.5%, respectively. The barcode combination of psbA-trnH+trnC-petN could identify 33 samples of the genus Syringa accurately and effectively with an identification rate of 87.5%. The 33 Syringa samples were divided into four groups: Group I is series Syringa represented by Syringa oblata; Group II is series Villosae represented by Syringa villosa; Group III is series Pubescentes represented by Syringa meyeri; and Group IV is section Ligustrina represented by Syringa reticulata subsp. pekinensis. These research results provided strong evidence that the combinatorial barcode of psbA-trnH+trnC-petN had high-efficiency identification ability and application prospects in species of the genus Syringa.