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The gamma-ray-induced random mutagenesis of an engineered β-carotene-producing Escherichia coli XL1-Blue resulted in the variant Ajou 45, which exhibits significantly enhanced β-carotene production. The whole-genome sequencing of Ajou 45 identified 55 mutations, notably including a reduction in the copy number of cyaA, encoding adenylate cyclase, a key enzyme regulating intracellular cyclic AMP (cAMP) levels. While the parental XL1-Blue strain harbors two copies of cyaA, Ajou 45 retains only one, potentially leading to reduced intracellular cAMP concentrations. This reduction may alleviate catabolite repression and redirect metabolic flux toward the β-carotene biosynthesis pathway. To validate this mechanistic insight, a targeted cyaA knockout was engineered in XL1-Blue, and its β-carotene production and growth phenotypes were compared with those of Ajou 45 and XL1-Blue. The findings demonstrated that a reduced cyaA copy number substantially enhances β-carotene biosynthesis by modulating cAMP-mediated regulatory networks. This study highlights the efficacy of integrating random mutagenesis with integrative genomic analysis for microbial strain engineering and presents a novel strategy for enhancing carotenoid production in E. coli. [ABSTRACT FROM AUTHOR]

Storing CO2 and converting it into valuable substances are crucial for addressing climate change. While poly(propylene carbonate) (PPC), formed through the copolymerization of CO2 and propylene oxide, holds promise in commercial applications, practical limitations arise due to inherent property constraints. Additionally, the lack of systematic research on PPC biodegradation complicates its post‐use disposal. In this study, we synthesized various polymers, including PPC homopolymers, PPC/castor oil star copolymers, and PPC/poly(l‐lactic acid) multiblock copolymers (PPC‐mb‐PLLAs), not only to mitigate the brittle properties of PPC but also to systematically explore their biodegradability. Both natural soil and industrial composting conditions were employed to assess the biodegradation of the polymers. Furthermore, metagenomic analysis identified the microorganisms responsible for polymer degradation, offering valuable insights into the mechanism of the biodegradation process. [ABSTRACT FROM AUTHOR]

Introduction Carotenoids are a class of isoprenoid derivatives and more than 700 carotenoids have been identified to date (Lee et al. 2003). They are biosynthesized by microorganisms, fungi, algae, and [...], We investigated the cytotoxic activities of crocin and crocetin, 2 major carotenoids isolated from the stigma of Crocus sativus (saffron), on 5 human cancer cell lines and proposed their possible anticancer mechanisms. Crocetin, a glycosylated carotenoid, showed approximately 5- to 18-fold higher cytotoxicity than crocin, a carboxylic carotenoid ([IC.sub.50] of 0.16-0.61 mmol/L for crocetin vs. 2.0-5.5 mmol/L for crocin). This suggests that structural differences account for the different efficacies between them. Fluorescence-activated cell sorting (FACS) analysis showed that crocetin induced a significant level of cellular reactive oxygen species (ROS) in HeLa cells, whereas crocin did not. This ROS induction supported the cytotoxicity of crocetin, but not of crocin. A significant activation of nuclear factor erythroid 2-related factor 2 (Nrf2) was observed in both HeLa cells treated with crocin and crocetin: a 3.0-fold increase by 1 mmol/L crocetin and a 1.6-fold increase by 0.8 mmol/L crocin compared to the control. Furthermore, both crocetin and crocin reduced the protein expression of lactate dehydrogenase A (LDHA), one of the targets for chemoprevention in cancer cells, by 34.2% and 10.5%, respectively, compared to the control in HeLa cells. These findings suggest that crocetin and crocin have different mechanisms for their observed cytotoxicity in cancer cell lines. Key words: crocin, crocetin, ROS, LDHA. Nous avons examine l'activite cytotoxique de deux carotenoides importants, l'un glycosyle (crocine) et l'autre, carboxyle (crocetine), isoles du stigmate de Crocus sativus, sur 5 lignees cellulaires cancereuses humaines, et nous avons propose de possibles mecanismes d'action anticancereuse. La crocetine etait environ de 5 a 18 fois plus cytotoxique que la crocine ([CI.sub.50] de 0.16-0.61 mmol/L pour la crocetine comparativement a 2.0 a 5.5 mmol/L pour la crocine), suggerant que les differences de structures sont responsables des differences d'efficacite. L'analyse par FACS a montre que la crocetine induisait un niveau significatif d'especes reactives d'oxygene (ERO) cellulaires chez les cellules HeLa, contrairement a la crocine. Cette induction d'ERO soutenait la cytotoxicite de la crocetine, contrairement a la crocine. Une activation significative de facteur nucleaire Nrf2 (nuclear factor E2-related factor 2) a ete observee chez les cellules HeLa traitees a la crocine et la crocetine : une augmentation de 3 fois par 1 mmol/L de crocetine et de 1.6 fois par 0.8 mmol/L de crocine, comparativement au controle. De plus, tant la crocetine que la crocine reduisaient l'expression de la lactate deshydrogenase A (LDHA), une des cibles de la chimioprevention du cancer, de 34.2 % et 10.5 % respectivement, comparativement au controle chez les cellules HeLa. Ces donnees suggerent de maniere irrefutable que la crocetine et la crocine exercent une activite cytotoxique envers les cellules cancereuses par l'intermediaire de differents mecanismes. [Traduit par la Redaction] Mots-cles: crocine, crocetine, ERO, LDHA.

Isoprenoids, which are natural compounds with diverse structures, possess several biological activities that are beneficial to humans. A major consideration in isoprenoid production in microbial hosts is that the accumulation of biosynthesized isoprenoid within intracellular membranes may impede balanced cell growth, which may consequently reduce the desired yield of the target isoprenoid. As a strategy to overcome this suggested limitation, we selected peroxisome membranes as depots for the additional storage of biosynthesized isoprenoids to facilitate increased isoprenoid production in Saccharomyces cerevisiae. To maximize the peroxisome membrane storage capacity of S.cerevisiae, the copy number and size of peroxisomes were increased through genetic engineering of the expression of three peroxisome biogenesis-related peroxins (Pex11p, Pex34p, and Atg36p). The genetically enlarged and high copied peroxisomes in S.cerevisiae were stably maintained under a bioreactor fermentation condition. The peroxisome-engineered S.cerevisiae strains were then utilized as host strains for metabolic engineering of heterologous protopanaxadiol pathway. The yields of protopanaxadiol from the engineered peroxisome strains were ca 78% higher than those of the parent strain, which strongly supports the rationale for harnessing the storage capacity of the peroxisome membrane to accommodate the biosynthesized compounds. Consequently, this study presents in-depth knowledge on peroxisome biogenesis engineering in S.cerevisiae and could serve as basic information for improvement in ginsenosides production and as a potential platform to be utilized for other isoprenoids. [ABSTRACT FROM AUTHOR]