Multiple gene integration to promote erythritol production on glycerol in Yarrowia lipolytica.

OBJECTIVE: Erythritol (1,2,3,4-butanetetrol) is a 4-carbon sugar alcohol that occurs in nature as a metabolite or storage compound. In this study, a multiple gene integration strategy was employed to enhance erythritol production in Y. lipolytica. RESULTS: The effects on the production of erythritol in Y. lipolytica of seven key genes involved in the erythritol synthesis pathway were evaluated individually, among which transketolase (TKL1) and transaldolase (TAL1) showed important roles in enhancing erythritol production. The combined overexpression of four genes (GUT1, TPI1, TKL1, TAL1) and disruption of the EYD1 gene (encoding erythritol dehydrogenase), resulted in produce approximately 40 g/L erythritol production from glycerol. Further enhanced erythritol synthesis was obtained by overexpressing the RKI1 gene (encoding ribose 5-phosphate isomerase) and the AMPD gene (encoding AMP deaminase), indicating for the first time that these two genes are also related to the enhancement of erythritol production in Y. lipolytica. CONCLUSIONS: A combined gene overexpression strategy was developed to efficiently improve the production of erythritol in Y. lipolytica, suggesting a great capacity and promising potential of this non-conventional yeast in converting glycerol into erythritol.

Biosynthesis of α-Pinene by Genetically Engineered Yarrowia lipolytica from Low-Cost Renewable Feedstocks.

α-Pinene, an important biologically active natural monoterpene, has been widely used in fragrances, medicines, and fine chemicals, especially, in high-density renewable fuels such as jet fuel. The development of an α-pinene production platform in a highly modifiable microbe from renewable substitute feedstocks could lead to a green, economical avenue, and sustainable biotechnological process for the biosynthesis of α-pinene. Here, we report engineering of an orthogonal biosynthetic pathway for efficient production of α-pinene in oleaginous yeast Yarrowia lipolytica that resulted in an α-pinene titer of 19.6 mg/L when using glucose as the sole carbon source, a significant 218-fold improvement than the initial titer. In addition, the potential of using waste cooking oil and lignocellulosic hydrolysate as carbon sources for α-pinene production from the engineered Y. lipolytica strains was analyzed. The results indicated that α-pinene titers of 33.8 and 36.1 mg/L were successfully obtained in waste cooking oil and lignocellulosic hydrolysate medium, thereby representing the highest titer reported to date in yeast. To our knowledge, this is also the first report related to microbial production of α-pinene from waste cooking oil and lignocellulosic hydrolysate.

Multicopy integrants of crt genes and co-expression of AMP deaminase improve lycopene production in Yarrowia lipolytica.

Lycopene has been broadly studied in recent decades due to its health benefits including cancer prevention, anti-atherogenic and anti-obesity effects, and modulation of the immune system. To obtain efficient synthesis of lycopene, extensive researches have been conducted in various microbial cells, including Yarrowia lipolytica, to heterologously produce lycopene using various genetic and metabolic engineering methods. In this study, the effects of copy numbers of lycopene synthesis genes, a variety of key central metabolic genes (especially AMP deaminase-encoding gene AMPD), and 5-L fermenter cultivation on lycopene production in Y. lipolytica were investigated and the engineered strains with significantly enhanced lycopene content (46-60 mg/g DCW) were achieved. It is therefore possible to make use of the obtained strains to meet the industrial demand of lycopene production on the basis of further genetic and process optimization.

The effect of dehydroepiandrosterone supplementation on ovarian response is associated with androgen receptor in diminished ovarian reserve women.

BACKGROUND: Diminished ovarian reserve(DOR) is associated with female infertility and poor response to ovarian stimulation. Our objective was to assess the effect of dehydroepiandrosterone(DHEA) on DOR women and to explore whether the improvement of ovarian response after DHEA supplementation was dependent on the expression levels of androgen receptor(AR). METHODS: A prospective cohort study was performed in the Department of Human Reproductive Medicine, Beijing Obstetrics and Gynecology Hospital during August 2014 to August 2016. 103 DOR women who completed the study were divided into the DHEA group (n = 53), which received DHEA supplementation (25 mg three times a day) for 8 weeks, and the control group (n = 50), which did not receive DHEA, before the IVF cycles. Serum hormone levels(FSH, LH, E2, T, DHEAs, AMH, INHB), antral follicle count(AFC) and the expression of AR and FSH receptor(FSHR) in granulosa cells(GCs) were measured, meanwhile ovarian response parameters and IVF outcomes were compared. The GCs from another 36 DOR women were cultured with different concentrations of DHEA in vitro. Then, we compared the expression of AR and FSHR in GCs according to the different numbers of oocytes retrieved both in DHEA and control group. RESULTS: In the present study, DHEA supplementation resulted in significantly higher levels of serum T(P = 0.047), DHEAs(P = 0.019) and AR mRNA expression in GCs(P = 0.049). In vitro experiment, the protein and mRNA expression of AR and FSHR in the preovulatory GCs were significantly increased in response to DHEA supplementation(P <0.05). No significant differences were found in ovarian reserve, ovarian response, or IVF outcomes between the two groups. Subgroup analyses showed the levels of AR and FSHR mRNA in GCs were significantly increased in DHEA group with ≥5 oocytes retrieved(P <0.05). CONCLUSION: DHEA supplementation can increase the expression of AR in preovulatory GCs both in vivo and in vitro. The selective beneficial effects of DHEA supplementation on ovarian response in DOR women may depend on the increasing expression of AR and FSHR in GCs. TRIAL REGISTRATION: The Chinese Clinical Trial Registry ( ChiCTR-IPR-15006126 ). Retrospectively Registered 19 March 2015.

miR-23a and miR-27a promote human granulosa cell apoptosis by targeting SMAD5.

In mammals, follicular atresia can be partially triggered by granulosa cell apoptosis. However, very little is known about the functions of miRNAs in granulosa cell apoptosis. We previously reported that hsa-mir-23a (miR-23a) and hsa-mir-27a (miR-27a) were highly expressed in the plasma of patients with premature ovarian failure, but the action of these two miRNAs in follicular development was unclear. In this study, we explored the roles of miR-23a and miR-27a in the granulosa cells of women undergoing in vitro fertilization/embryo transfer. Using Hoechst staining, we found that miR-23a and miR-27a promoted apoptosis in human granulosa cells. In addition, the Western blotting results suggested that the miR-23a/miR-27a-mediated apoptosis occurred via the FasL-Fas pathway. Based on the results of a luciferase-reporter assay and quantitative RT-PCR and Western blotting analyses, we found that SMAD5 is a target gene of both miR-23a and miR-27a. Furthermore, knocking down SMAD5 expression increased the rate of apoptosis, as well as the levels of Fas, FasL, cleaved caspase-8, and cleaved caspase-3 protein. Taken together, these data suggest that miR-23a and miR-27a target SMAD5 and regulate apoptosis in human granulosa cells via the FasL-Fas pathway. These findings provide an improved understanding of the mechanisms underlying granulosa cell apoptosis, which could potentially be used for future clinical applications.

The dynamic changes of anti-Mullerian hormone and inhibin B during controlled ovarian hyperstimulation in decreased ovarian reserve women and the effect on clinical outcome.

OBJECTIVE: To investigate the dynamics of anti-Mullerian hormone (AMH) and inhibin B (INHB) levels during controlled ovarian hyperstimulation (COH) in women with decreased ovarian reserve (DOR), and assess the effect of these dynamic changes on the prediction of clinical outcome in in-vitro fertilization (IVF). METHODS: A total of 124 women undergoing IVF cycles were divided into normal ovarian reserve (NOR) and DOR groups. AMH and INHB levels were measured in serum on menstrual cycle day 2 or 3 (D2/3), day 5 of stimulation (D5), hCG day (D-hCG) and follicular fluid (FF) on oocyte retrieval day. RESULTS: Serum AMH levels were gradually decreased while INHB levels were gradually increased from D2/3 to D-hCG during the COH in both groups. Serum AMH, INHB levels on D2/3 and FF AMH, INHB levels were highly positively correlated with AFC and oocytes retrieval. Multivariate logistic regression analysis revealed that clinical pregnancy did not directly correlate with serum and FF AMH and INHB levels. CONCLUSION: Serum AMH and INHB levels were not directly related to clinical pregnancy, dynamic serum AMH and IHNB levels were positively correlated with COH outcomes.