Contribution of Secondary Structure Changes to the Surface Activity of Proteins

Engineering Pichia pastoris for Efficient De Novo Synthesis of 2'-Fucosyllactose

2'-Fucosyllactose (2'-FL), the most abundant in human milk oligosaccharides (HMOs), is a nutrient of great importance. As a safe organism widely used in industries, Pichia pastoris was tested here for 2'-FL production. The de novo biosynthesis pathway of 2'-FL was constructed using genome-editing technology based on CRISPR-Cas9 with an initial titer of 1.01 g/L. Introducing N-terminal SUMO or Ub tag to FucT2 and the transporter CDT2 from Neurospora crassa into P. pastoris was found to improve 2'-FL production. Then, modular metabolic engineering was conducted to improve 2'-FL production, enhancing the GTP supply module, NADPH regeneration module, and precursor supply module. Subsequently, the key enzyme FucT2 was semirationally designed to further increase 2'-FL production. Finally, the 2'-FL production by engineered P. pastoris was scaled up to the 3 L fermenter in fed-batch mode, resulting in a titer of 22.35 g/L that is the highest by P. pastoris. The results prove the effectiveness of the metabolic engineering strategies and demonstrate that P. pastoris could be a potential chassis to produce HMOs.

Synergistic growth suppression of Fusarium oxysporum MLY127 through Dimethachlon Nanoencapsulation and co-application with Bacillus velezensis MLY71

Fusarium oxysporum is a destructive plant pathogen with robust survival mechanisms, complicating control efforts. This study aimed to develop nanoformulated fungicides, screen antagonistic bacteria, and evaluate their combined efficacy. A novel self-emulsifying nanoemulsion (DZW) was formulated using zein and benzaldehyde-modified wheat gluten (BgWG) as carriers for dimethachlon (DTN). The preparation process optimized material ratios and emulsification techniques. Concurrently, antagonistic bacterial strains against F. oxysporum were screened via the plate standoff method, identifying Bacillus velezensis MLY71 as both antagonistic and compatible with DTN. The DZW nanoemulsion achieved a particle size of 93.22 nm, an encapsulation efficiency (EE) of 90.57%, and a DTN loading capacity (LC) of 67.09%, with sustained release over 96 h. The combination of DTN (0.04 mg·mL⁻¹) and B. velezensis MLY71 (1 × 10⁴ CFU·mL⁻¹) achieved a 76.66% inhibition rate against F. oxysporum MLY127, 1.71 times greater than DTN alone, indicating significant synergy. At a DTN concentration of 0.20 mg·mL⁻¹, the combination of DZW and MLY71 showed a synergy coefficient of 1.33. This synergy was also observed in soil environments, indicating its adaptability for controlling soil-borne pathogens. As sustainable management continues to gain attention in agricultural disease control, this study offers a promising strategy for achieving higher efficacy with the same fungicide dose or satisfactory control with reduced fungicide application. The excellent drug-loading performance of BgWG also expanded the applications of the wheat by-product gluten.

Structural changes and functional characteristics of common vetch isolate proteins altered by different pH-shifting treatments

To investigate protein structure and functional changes, common vetch protein isolate (CVPI) during pH-shifting were performed. Results showed secondary and tertiary structures of CVPI were improved during these treatments compared with the pH 7.0. Scanning electron microscopy showed the microstructure was changed from lamellar to spherical granular and rod-like structure during pH - shifting. Under 8 pH treatments (pH 2.0, 3.0, 12.0, 2.0 → 7.0, 3.0 → 7.0, 12.0 → 7.0, 11.0 → 9.0 and 11.0 → 7.0), the average particle sizes were smaller and from 82 to 146 nm. Under 8 pH treatments (pH 2.0, 3.0, 11.0, 12.0, 11.0 → 9.0, 11.0 → 7.0,12.0 → 9.0 and 12.0 → 7.0), the protein solubility was higher and from 63 to 86 %. Under 3 pH treatments (pH 2.0, 11.0 and 12.0), the emulsion activity index and emulsion stability index was higher and from 40 to 60 m2/g and from 54 to 97 min. Under 5 pH treatments (pH 2.0, 12.0, 11.0 → 9.0, 12.0 → 9.0 and 12.0 → 7.0), the foaming capacity and foaming stability was higher and from 145 to 185 % and from 67 to 82 %. Therefore, the pH - shifting treatment gave the CVPI improved characteristics in structural and functional properties.

Enhancing lactose recognition of a key enzyme in 2'-fucosyllactose synthesis: α-1,2-fucosyltransferase

BACKGROUND

2'-Fucosyllactose, a representative oligosaccharide in human milk, is an emerging and promising food and pharmaceutical ingredient due to its powerful health benefits, such as participating in immune regulation, regulation of intestinal flora, etc. To enable economically viable production of 2'-fucosyllactose, different biosynthesis strategies using precursors and pathway enzymes have been developed. The α-1,2-fucosyltransferases are an essential part involved in these strategies, but their strict substrate selectivity and unsatisfactory substrate tolerance are one of the key roadblocks limiting biosynthesis.

RESULTS

To tackle this issue, a semi-rational manipulation combining computer-aided designing and screening with biochemical experiments were adopted. The mutant had a 100-fold increase in catalytic efficiency compared to the wild-type. The highest 2'-fucosyllactose yield was up to 0.65 mol mol^-1 lactose with a productivity of 2.56 g mL^-1  h^-1 performed by enzymatic catalysis in vitro. Further analysis revealed that the interactions between the mutant and substrates were reduced. The crucial contributions of wild-type and mutant to substrate recognition ability were closely related to their distinct phylotypes in terms of amino acid preference.

CONCLUSION

It is envisioned that the engineered α-1,2-fucosyltransferase could be harnessed to relieve constraints imposed on the bioproduction of 2'-fucosyllactose and lay a theoretical foundation for elucidating the substrate recognition mechanisms of fucosyltransferases. © 2022 Society of Chemical Industry.

Enhancing heterologous expression of a key enzyme for the biosynthesis of 2'-fucosyllactose

BACKGROUND

2'-Fucosyllactose (2'-FL) is the most abundant human milk oligosaccharide (HMO) in human milk and has important physiological functions. The market demand of 2'-FL is continuing to grow, but high production cost has limited its availability. To solve the dilemma, biosynthesis of 2'-FL has been proposed and is considered the most promising pathway for massive production. α-1,2-Fucosyltransferase is one of the key elements involved in its biosynthesis, but the limited intracellular accumulation and unstable properties of α-1,2-fucosyltransferases when expressed in host strains have become a major hurdle for the effective biosynthesis of 2'-FL.

RESULTS

A combinatorial engineering strategy of synergic modification of ribosome binding site, fusion peptide and enzyme gene was leveraged to enhance the soluble expression of α-1,2-fucosyltransferases and promote enzyme activity. The preferable combination was to employ an optimized ribosome binding site region to drive 3 × FLAG as a fusion partner along with the α-1,2-fucosyltransferase for expression in Escherichia coli (DE3) PlySs, and protein yield and enzyme activity were remarkably improved by 11.51-fold and 13.72-fold, respectively.

CONCLUSION

After finely tuning the synergy among different elements, the abundant protein yield and high enzyme activity confirmed that the drawbacks of heterologous expression in α-1,2-fucosyltransferase had been properly addressed. A suitable external environment further drives the efficient synthesis of α-1,2-fucosyltransferases. To our knowledge, this is the first report of a systematic and effective modification of α-1,2-fucosyltransferase expression, which could potentially serve as a guideline for industrial application. © 2022 Society of Chemical Industry.