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In this study, the lycopene β-cyclase (LCYb) and lycopene ε-cyclase (LCYe) genes were cloned from maize, and the encoded products were analyzed by bioinformatics methods. After expression in Escherichia coli, the catalytic properties of LCYb and LCYe from maize were explored by color complementation and product analysis experiments. The results of sequence analysis showed that the full-length cDNA of maize LCYb and LCYe were 1 470 and 1 611 bp, respectively, which were more than 90% homologous to those of sorghum and millet. LCYe and LCYb proteins were successfully purified by fusion expression with glutathione thiotransferase tags. The results of color complementation test and high performance liquid chromatography (HPLC) analysis showed that maize LCYb had catalytic activity on β-ring, could cyclize both ends of lycopene to form β-carotene, and had very weak ε-ring catalytic activity, which could form α-carotene through the intermediate γ-carotene. Maize LCYe was also found to able to catalyze both ends of lycopene to form ε-carotene. This study can lay a foundation for exploring the molecular mechanism of the regulation of maize carotenoid.

Abstract Background Xanthophylls are a large class of carotenoids that are found in a variety of organisms and play particularly important roles in the light-harvesting and photoprotection processes of plants and algae. Violaxanthin is an important plant-derived xanthophyll with wide potential applications in medicines, foods, and cosmetics because of its antioxidant activity and bright yellow color. To date, however, violaxanthins have not been produced using metabolically engineered microbes on a commercial scale. Metabolic engineering for microbial production of violaxanthin is hindered by inefficient synthesis pathway in the heterologous host. We systematically optimized the carotenoid chassis and improved the functional expression of key enzymes of violaxanthin biosynthesis in Escherichia coli. Results Co-overexpression of crtY (encoding lycopene β-cyclase), crtZ (encoding β-carotene 3-hydroxylase), and ZEP (encoding zeaxanthin epoxidase) had a notable impact on their functions, resulting in the accumulation of intermediate products, specifically lycopene and β-carotene. A chassis strain that did not accumulate the intermediate was optimized by several approaches. A promoter library was used to optimize the expression of crtY and crtZ. The resulting strain DZ12 produced zeaxanthin without intermediates. The expression of ZEP was further systematically optimized by using DZ12 as the chassis host. By using a low copy number plasmid and a modified dithiol/disulfide system, and by co-expressing a full electron transport chain, we generated a strain producing violaxanthin at about 25.28 ± 3.94 mg/g dry cell weight with decreased byproduct accumulation. Conclusion We developed an efficient metabolically engineered Escherichia coli strain capable of producing a large amount of violaxanthin. This is the first report of a metabolically engineered microbial platform that could be used for the commercial production of violaxanthin.

In order to select the varieties suitable for processing blueberry crispy, the quality evaluation of freeze-dried blueberry crispy was carried out. In this study, eight Highbush blueberries and Rabbiteye blueberries varieties in Jiangsu Province were used as raw materials, and were prepared as blueberry crispy by vacuum freeze-drying, and 18 quality indexes such as water content, total sugar, scavenging ability of DPPH free radical, hardness, etc, were determined, and the quality of the blueberry crispy was comprehensively evaluated by principal component analysis. The results showed that the coefficients of variation of sugar-acid ratio and total acid of different varieties of blueberry crispy were larger, with the value of 57.89% and 40.25%, respectively. Principal component analysis showed that the glucose content, anthocyanoside content, total flavonoid content, total antioxidant activity of AEAC, moisture content of dry samples, output rate and hardness were determined as representative indexes for the evaluation of the quality of blueberry brittle grains. Then, the comprehensive quality evaluation model was established. Based on the comprehensive quality score of each variety, the top three blueberry varieties were Legacy, Brightwell and Climax, and the others varieties had negative scores. This indicated that these three kinds of blueberries were more suitable for dry processing as blueberry crispy, among which the Legacy variety was the better. The results of the study provide a basis for the screening and quality analysis of blueberry varieties for dry processing. [ABSTRACT FROM AUTHOR]

Hyperlipidemia is a metabolic disorder characterized by abnormal lipid metabolism, resulting in lipid accumulation in the plasma. According to reports, medicinal and edible plants can reduce the risk of metabolic diseases such as hyperlipidemia. This study investigates the effects and mechanisms of Astragalus membranaceus extract (AME), Hippophae rhamnoides L. extract (HRE), and Taraxacum mongolicum Hand. Mazz extract (TME) on hyperlipidemia. Active compounds and potential gene targets of AME, HRE, and TME were screened using LC-MS and TCMSP databases, and hyperlipidemia targets were detected from the OMIM and DisGeNet databases. A drug-target pathway disease network was constructed through protein interactions, GO enrichment, and KEGG pathway analysis. Finally, the lipid-lowering effects of three extracts were validated through in vitro HepG2 cell and in vivo animal experiments. The results show that LC-MS and network pharmacology methodologies identified 41 compounds and 140 targets. KEGG analysis indicated that the PI3K-Akt and MAPK signaling pathways significantly treat hyperlipidemia with AHT. In vitro experiments have shown that AHT is composed of a ratio of AME:HRE:TME = 3:1:2. HepG2 cell and animal experiments revealed that AHT exhibits strong lipid-lowering and antioxidant properties, significantly regulating the levels of total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC). It is worth noting that AHT can effectively downregulate the protein expression levels of p-AKT/AKT and p-PI3K/PI3K and upregulate the protein expression levels of p-AMPK/AMPK and SIRT1, verifying the results predicted by network pharmacology. This study presents a novel approach to utilizing these natural plant extracts as safe and effective treatments for hyperlipidemia. [ABSTRACT FROM AUTHOR]

To prepare different types of lutein nanostructured lipid carriers (LNLs) using chitosan (CS), chitosan-epigallocatechin gallate covalent (C-CS-EGCG), and chitosan-epigallocatechin gallate ester non-covalent (Non-C-CS-EGCG) modifications combined with high-pressure microfluidization. A simulated colonic digestion model was established to investigate the stability and interaction with gut microbiota of these modified lutein nanostructured lipid carriers. Results showed that after 24 hours of simulated in vitro colonic fermentation, the lutein content in CS-LNLs significantly decreased (P<0.05) compared to other treatment groups. Except for lutein and CS-LNLs, the total sugar content in the fermentation supernatant significantly decreased (P<0.05) in other treatment groups, while the total polyphenol content in C-CS-EGCG-LNLs and Non-C-CS-EGCG-LNLs showed an opposite trend. After 24 hours of fermentation, the production of acetic acid and propionic acid significantly increased (P<0.05) in all treatment groups except the LUT group, with the acetic acid concentration reaching 17.18±0.60 mmol/L in the C-CS-EGCG-LNLs group. The lactic acid concentration reached 2.87±0.05 mmol/L, significantly higher (P<0.05) than the blank control group (BLK) by 7.55 times. The three different types of modified lutein nanostructured lipid carriers had a significant impact on the gut microbiota structure. The relative abundance of Bacteroides, Bifidobacterium, and Faecalibacterium significantly increased (P<0.05) in CS-LNLs, C-CS-EGCG- LNLs, and Non-C-CS-EGCG-LNLs, while C-CS-EGCG-LNLs enriched more Veillonella. Conclusion: Compared to other modification groups, C-CS-EGCG-LNLs had significant intestinal microbial structural differentiation in the colon digestive phase of nanoliposomes. [ABSTRACT FROM AUTHOR]