Henan Institute of Science & Technology

Utilizing synthetic biology techniques to construct recombinant engineered cells for the synthesis of paclitaxel and its key precursors has emerged as an effective method to address the supply-demand imbalance and protect rare plant resources. Taxadiene, a critical precursor of paclitaxel, exhibits limited yield in eukaryotic systems, constraining its biosynthetic potential. Previous research has demonstrated that glycosylation modifications in Saccharomyces cerevisiae substantially impact the regulation of exogenous protein expression. In this study, we found that knocking out endogenous protein glycosylation genes in the chassis significantly improved the expression of heterologous proteins, especially the key taxadiene synthase (TS), and thereby increased the yield of taxadiene. In particular, we identified that the deletion of the glycosyltransferase gene mnn11 increased taxadiene production levels by 65.2 %. The subsequent multi-copy integration of the key enzyme taxadiene synthase further elevated taxadiene production levels in shake flasks by more than 3-fold, reaching 113.5 mg/L. Moreover, the enhancement of geranylgeranyl diphosphate synthesis-related expression modules resulted in a 2.69-fold increase in taxadiene yield, to 420.4 mg/L. Following the optimization of fed-batch fermentation conditions, taxadiene production levels of up to 1.26 g/L were achieved, representing a 63-fold improvement over that obtained with the initial strain. Our findings provide valuable insights into enhancing heterologous taxadiene production efficiency by blocking endogenous protein glycosylation modifications in S. cerevisiae, establishing a critical precedent for improving compatibility between natural product synthesis and microbial cell factories.

This study explored the structural and physicochemical properties of green wheat kernel starch (GWKS) and their effect on Pickering emulsion performance with polyphenol complexes. Compared to mature wheat starch (WS), GWKS had lower amylose content (28.20 ± 0.27%), greater branching (4.91%), and longer amylopectin chains, resulting in more double-helix structures but lower crystallinity. These traits gave GWKS better swelling power and thermal stability but weaker gel strength and slower retrogradation. For polyphenol-starch complexes, tannic acid (TA) bound strongly to GWKS, improving interfacial wettability (contact angle ∼90°), while gallic acid (GA) and epigallocatechin gallate (EGCG) failed to stabilize GWKS-based emulsions. GWKS-TA emulsion showed superior stability, with fine droplets (D₅₀ = 24.19 μm) and a strong elastic gel network, outperforming WS-based emulsions. The structural predominance of the branched-chain network in immature starch governs its intrinsic properties and underpins the enhanced stability of GWKS-TA emulsions, offering new pathways for advanced processing and high-value applications.

This study aimed to assess the effects of four single modifiers-transglutaminase (0.05%-0.25%), Artemisia sphaerocephala gum (0.2%-1.0%), gluten (5%-25%) and egg pulp (2%-10%) on the basis of sorghum-wheat flour weight (w/w)-on the physicochemical characteristics of sorghum-wheat mixed flour, dough and steamed bread. The results demonstrated that appropriate amounts, specifically 0.15% transglutaminase, 0.6% Artemisia sphaerocephala gum, 20% gluten and 8% egg pulp, significantly decreased the peak viscosity of the mixed flour as well as the hardness of the mixed dough and steamed bread, with the lowest values of 861.09 mPa·s, 7.22 N and 54.36 N, respectively, observed in the samples containing 20% gluten. These outcomes are due to the increased content of bound water and α-helical and β-folded structures in the dough. The highest sensory score of 81.4 was obtained for the steamed bread containing 0.15% transglutaminase. Nevertheless, the flavor of sorghum-wheat-based steamed breads remains suboptimal and requires further optimization.