BACKGROUND: Surfactin, a green lipopeptide bio-surfactant, exhibits excellent surface, hemolytic, antibacterial, and emulsifying activities. However, a lack of clear understanding of the synthesis regulation mechanism of surfactin homologue components has hindered the customized production of surfactin products with different biological activities. RESULTS: In this study, exogenous valine and 2-methylbutyric acid supplementation significantly facilitated the production of C14-C15 surfactin proportions (up to 75% or more), with a positive correlation between the homologue proportion and fortified concentration. Subsequently, the branched-chain amino acid degradation pathway and the glutamate synthesis pathway are identified as critical pathways in regulating C14-C15 surfactin synthesis by transcriptome analysis. Overexpression of genes bkdAB and glnA resulted in a 1.4-fold and 1.3-fold increase in C14 surfactin, respectively. Finally, the C14-rich surfactin was observed to significantly enhance emulsification activity, achieving an EI24 exceeding 60% against hexadecane, while simultaneously reducing hemolytic activity. Conversely, the C15-rich surfactin demonstrated an increase in both hemolytic and antibacterial activities. CONCLUSION: This study presents the first evidence of a potential connection between surfactin homologue synthesis and the conversion of glutamate and glutamine, providing a theoretical basis for targeting the synthesis regulation and structure-activity relationships of surfactin and other lipopeptide compounds.
Fatty Acids , Surface-Active Agents , Fatty Acids/metabolism , Surface-Active Agents/metabolism , Glutamic Acid/metabolism , Lipopeptides , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/metabolism , Peptides, Cyclic/chemistry , Bacillus subtilis/genetics
The multiplane augmented reality (AR) head-up display (HUD) is important in improving driving safety and comfort. In this paper, we propose an AR-HUD with switchable display modes based on polymer dispersed liquid crystal (PDLC) and lens holographic optical elements (HOEs), which can provide two display modes: the dual-virtual-image mode and the virtual-real-image mode. The dual-virtual-image mode can produce two virtual images at different depths, which can provide a better sense of reality integration for the driver to improve driving safety and comfort. The virtual-real-image mode can produce one far virtual image and one near real image at different depths, and it provides a larger eye box (EB) for both driver and passengers in the car and a higher image contrast. The two display modes can be switched by an electronically controlled scattering module consisting of a pair of PDLC films. The proposed AR-HUD system is compact and equipped with multiplane display and mode-switching functions, and is expected to be applied in the future.
The O-glycosylation of polyphenols for the synthesis of glycosides has garnered substantial attention in food research applications. However, the practical utility of UDP-glycosyltransferases (UGTs) is significantly hindered by their low catalytic efficiency and suboptimal regioselectivity. The concurrent optimization of the regioselectivity and activity during the glycosylation of polyphenols presents a formidable challenge. Here, we addressed the long-standing activity-regioselectivity tradeoff in glycosyltransferase UGTBL1 through systematic enzyme engineering. The optimal combination of mutants, N61S/I62M/D63W/A208R/P218W/R282W (SMWRW1W2), yielded a 6.1-fold improvement in relative activity and a 17.3-fold increase in the ratio of gastrodin to para-hydroxybenzyl alcohol-4'-O-ß-glucoside (with 89.5% regioselectivity for gastrodin) compared to those of the wild-type enzyme and ultimately allowed gram-scale production of gastrodin (1,066.2 mg/L) using whole-cell biocatalysis. In addition, variant SMWRW1W2 exhibited a preference for producing phenolic glycosides from several substrates. This study lays the foundation for the engineering of additional UGTs and the practical applications of UGTs in regioselective retrofitting.
Benzyl Alcohols , Glycosides , Glycosyltransferases , Uridine Diphosphate , Glucosides , Phenols , Polyphenols
A super multi-view (SMV) near-eye display (NED) effectively provides depth cues for three-dimensional (3D) display by projecting multiple viewpoint or parallax images onto the retina simultaneously. Previous SMV NED have suffered from a limited depth of field (DOF) due to a fixed image plane. In this paper, a holographic SMV Maxwellian display based on depth segmentation is proposed to enhance the DOF. The proposed approach involves capturing a set of parallax images and their corresponding depth maps. According to the depth maps, the parallax images are segmented into N sub-parallax images at different depth ranges. These sub-parallax images are then projected onto N image-recording planes (IRPs) of the corresponding depth for hologram computation. The wavefront at each IRP is calculated by multiplying the sub-parallax images with the corresponding spherical wave phases. Then, they are propagated to the hologram plane and added together to form a DOF-enhanced hologram. The simulation and experimental results are obtained to validate the effectiveness of the proposed method in extending the DOF of the holographic SMV displays, while accurately preserving occlusion.
