Improving Acetic Acid and Furfural Resistance of Xylose-Fermenting Saccharomyces cerevisiae Strains by Regulating Novel Transcription Factors Revealed via Comparative Transcriptomic Analysis.

Acetic acid and furfural are the two prevalent inhibitors coexisting with glucose and xylose in lignocellulosic hydrolysate. The transcriptional regulations of Saccharomyces cerevisiae in response to acetic acid (Aa), furfural (Fur), and the mixture of acetic acid and furfural (Aa_Fur) were revealed during mixed glucose and xylose fermentation. Carbohydrate metabolism pathways were significantly enriched in response to Aa, while pathways of xenobiotic biodegradation and metabolism were significantly enriched in response to Fur. In addition to these pathways, other pathways were activated in response to Aa_Fur, i.e., cofactor and vitamin metabolism and lipid metabolism. Overexpression of Haa1p or Tye7p improved xylose consumption rates by nearly 50%, while the ethanol yield was enhanced by nearly 8% under acetic acid and furfural stress conditions. Co-overexpression of Haa1p and Tye7p resulted in a 59% increase in xylose consumption rate and a 12% increase in ethanol yield, revealing the beneficial effects of Haa1p and Tye7p on improving the tolerance of yeast to mixed acetic acid and furfural.IMPORTANCE Inhibitor tolerance is essential for S. cerevisiae when fermenting lignocellulosic hydrolysate with various inhibitors, including weak acids, furans, and phenols. The details regarding how xylose-fermenting S. cerevisiae strains respond to multiple inhibitors during fermenting mixed glucose and xylose are still unknown. This study revealed the transcriptional regulation mechanism of an industrial xylose-fermenting S. cerevisiae strain in response to acetic acid and furfural. The transcription factor Haa1p was found to be involved in both acetic acid and furfural tolerance. In addition to Haa1p, four other transcription factors, Hap4p, Yox1p, Tye7p, and Mga1p, were identified as able to improve the resistance of yeast to these two inhibitors. This study underscores the feasibility of uncovering effective transcription factors for constructing robust strains for lignocellulosic bioethanol production.

Improving xylitol yield by deletion of endogenous xylitol-assimilating genes: a study of industrial Saccharomyces cerevisiae in fermentation of glucose and xylose.

Engineered Saccharomyces cerevisiae can reduce xylose to xylitol. However, in S.cerevisiae, there are several endogenous enzymes including xylitol dehydrogenase encoded by XYL2, sorbitol dehydrogenases encoded by SOR1/SOR2 and xylulokinase encoded by XKS1 may lead to the assimilation of xylitol. In this study, to increase xylitol accumulation, these genes were separately deleted through CRISPR/Cas9 system. Their effects on xylitol yield of an industrial S. cerevisiae CK17 overexpressing Candida tropicalis XYL1 (encoding xylose reductase) were investigated. Deletion of SOR1/SOR2 or XKS1 increased the xylitol yield in both batch and fed-batch fermentation with different concentrations of glucose and xylose. The analysis of the transcription level of key genes in the mutants during fed-batch fermentation suggests that SOR1/SOR2 are more crucially responsible for xylitol oxidation than XYL2 under the genetic background of S.cerevisiae CK17. The deletion of XKS1 gene could also weaken SOR1/SOR2 expression, thereby increasing the xylitol accumulation. The XKS1-deleted strain CK17ΔXKS1 produced 46.17 g/L of xylitol and reached a xylitol yield of 0.92 g/g during simultaneous saccharification and fermentation (SSF) of pretreated corn stover slurry. Therefore, the deletion of XKS1 gene provides a promising strategy to meet the industrial demands for xylitol production from lignocellulosic biomass.

Comparison of neoadjuvant chemoradiotherapy and neoadjuvant chemotherapy for esophageal cancer: a meta-analysis.

Aim: To compare the clinical efficacy of neoadjuvant chemoradiotherapy (nCRT) and neoadjuvant chemotherapy (nCT) for esophageal cancer. Methods: Randomized controlled trials reporting on the comparison of nCRT and nCT for esophageal cancer were identified. Results: Three eligible randomized controlled trials were identified and included with a total of 375 patients (189 nCRT, 186 nCT). Outcomes showed that compared with nCT group, R0 resection and pathologic complete response (pCR) rates were significantly increased in nCRT group. However, no significant difference was seen in 3- and 5-year progression-free survival or 3- and 5-year overall survival. Conclusion: The addition of radiotherapy to neoadjuvant chemotherapy results in higher R0 resection rate and pCR rate, without significantly impacting survival.

Comparison of elective nodal irradiation and involved-field irradiation in esophageal squamous cell carcinoma: a meta-analysis.

It remains controversial whether radical radiotherapy in patients with esophageal squamous cell carcinoma (ESCC) still requires elective nodal irradiation (ENI), or only involved-field irradiation (IFI). In this study, a meta-analysis was conducted to compare ENI and IFI in the treatment of ESCC, in order to provide guidance for clinical practice. Literature on the use of ENI and IFI in the treatment of ESCC was retrieved, and the last access date was 31 December 2017. A meta-analysis was performed to evaluate the relative advantages and disadvantages of using ENI and IFI. Ten studies, involving a total of 1348 patients, were included in this analysis; of these, 605 patients underwent radiotherapy only, and 743 underwent radiochemotherapy. There was no significant difference in the 1-, 2- or 3-year local control rates between ENI and IFI, or in the 1-, 2- or 3-year overall survival rates. However, the incidences of ≥Grade 3 acute esophagitis and pneumonia were significantly lower in the IFI group. There were no differences in the rates of ≥Grade 3 myelosuppression or of out-field recurrence or metastasis between these two groups. Thus, neither local control rates nor overall survival rates differed significantly between the ENI and IFI groups, but in the latter group, incidences of severe radiation esophagitis and pneumonia were significantly lower. IFI was not associated with an increase in out-field recurrence or metastasis.

Relationship between EGFR over-expression and clinicopathologic characteristics in squamous cell carcinoma of the esophagus: a meta-analysis.

Over-expression of epidermal growth factor receptor (EGFR) has been identified as a common feature associated with clinical outcome in many types of cancer, including squamous cell carcinoma of the oesophagus (SCCO). However, the clinical importance of EGFR over-expression in SCCO remains unsettled as conflicting results exist. Therefore we carried out the present meta-analysis of published studies for clarification. A total of 13 studies including 1,150 patients were enrolled. EGFR over-expression was positive in 722 of these cases. With EGFR over-expression, patients had higher depth of invasion, vascular invasion, and poor prognosis. However, expression had no relation with degree of differentiation, histological grade, lymph node metastasis, clinical stage or lymphatic invasion. EGFR over-expression is probably a valuable predictor for the T stage, vascular invasion and OS, and it could be used as a poor prognosis indicator for the esophageal SCC patients. Targeting therapy to EFGR should be considered to the combined treatment in SCCO.