Efficient production of retinol in Yarrowia lipolytica by increasing stability using antioxidant and detergent extraction.

The demand for bio-based retinol (vitamin A) is currently increasing, however its instability represents a major bottleneck in microbial production. Here, we developed an efficient method to selectively produce retinol in Yarrowia lipolytica. The ß-carotene 15,15'-dioxygenase (BCO) cleaves ß-carotene into retinal, which is reduced to retinol by retinol dehydrogenase (RDH). Therefore, to produce retinol, we first generated ß-carotene-producing strain based on a high-lipid-producer via overexpressing genes including heterologous ß-carotene biosynthetic genes, GGS1F43I mutant of endogenous geranylgeranyl pyrophosphate synthase isolated by directed evolution, and FAD1 encoding flavin adenine dinucleotide synthetase, while deleting several genes previously known to be beneficial for carotenoid production. To produce retinol, 11 copies of BCO gene from marine bacterium 66A03 (Mb.Blh) were integrated into the rDNA sites of the ß-carotene overproducer. The resulting strain produced more retinol than retinal, suggesting strong endogenous promiscuous RDH activity in Y. lipolytica. The introduction of Mb.Blh led to a considerable reduction in ß-carotene level, but less than 5% of the consumed ß-carotene could be detected in the form of retinal or retinol, implying severe degradation of the produced retinoids. However, addition of the antioxidant butylated hydroxytoluene (BHT) led to a >20-fold increase in retinol production, suggesting oxidative damage is the main cause of intracellular retinol degradation. Overexpression of GSH2 encoding glutathione synthetase further improved retinol production. Raman imaging revealed co-localization of retinol with lipid droplets, and extraction of retinol using Tween 80 was effective in improving retinol production. By combining BHT treatment and extraction using Tween 80, the final strain CJ2104 produced 4.86 g/L retinol and 0.26 g/L retinal in fed-batch fermentation in a 5-L bioreactor, which is the highest retinol production titer ever reported. This study demonstrates that Y. lipolytica is a suitable host for the industrial production of bio-based retinol.

An immune-responsive Serpin regulates the melanization cascade in Drosophila.

In arthropods, the melanization reaction is associated with multiple host defense mechanisms leading to the sequestration and killing of invading microorganisms. Arthropod melanization is controlled by a cascade of serine proteases that ultimately activates the enzyme prophenoloxidase (PPO), which, in turn, catalyzes the synthesis of melanin. Here we report the biochemical and genetic characterization of a Drosophila serine protease inhibitor protein, Serpin-27A, which regulates the melanization cascade through the specific inhibition of the terminal protease prophenoloxidase-activating enzyme. Our data demonstrate that Serpin-27A is required to restrict the phenoloxidase activity to the site of injury or infection, preventing the insect from excessive melanization.

Visual Impairment of Korean Population: Prevalence and Impact on Mental Health.

PURPOSE: We identified the prevalence and sociodemographic characteristics of people with visual impairment (VI), and determined the relationship between VI and mental health in the Korean population. METHODS: This is a cross-sectional study using the database of the Korean National Health and Nutrition Examination Survey from 2008 through 2012. A total of 28,392 participants at 19 years of age or older with data of visual acuity and mental health questionnaire was included. Prevalence of VI and its association with sociodemographic factors were analyzed. Multivariate regression analyses were conducted to determine the association of VI with mental health. RESULTS: Estimated prevalence of VI was 0.43% (95% confidence interval [CI], 0.35-0.52%) in adults aged 19 years and over. After adjusting for sex, the VI group was significantly older (P < 0.001). After adjusting for age and sex, the VI group showed increased odds ratios (ORs) for diabetes mellitus (P < 0.001), lower education (P < 0.001), no occupation (P = 0.046), restricted daily activity (P < 0.001), and being single (P = 0.002) compared to the control group. After adjusting for covariates, VI was not associated with any of mental health parameters (OR, 0.88 [95% CI, 0.53-1.47] for depressive symptom; 1.38 [0.91-2.09] for suicidal ideation; 1.26 [0.82-1.94] for perceived stress). However, restricted daily activity was the strongest risk factor for poor mental health (OR, 2.49 [2.22-2.79] for depressive symptom; 2.77 [2.51-3.06] for suicidal ideation; 2.30 [2.09-2.54] for perceived stress). CONCLUSIONS: Visually impaired people showed significantly unfavorable sociodemographic status. Although VI was not directly associated with mental health, restricted daily activity and poor sociodemographic factors found in visually impaired people increased risk for poor mental health.