Genomic and metabolic analysis of Komagataeibacter xylinus DSM 2325 producing bacterial cellulose nanofiber.

Bacterial cellulose nanofiber (CNF) is a polymer with a wide range of potential industrial applications. Several Komagataeibacter species, including Komagataeibacter xylinus as a model organism, produce CNF. However, the industrial application of CNF has been hampered by inefficient CNF production, necessitating metabolic engineering for the enhanced CNF production. Here, we present complete genome sequence and a genome-scale metabolic model KxyMBEL1810 of K. xylinus DSM 2325 for metabolic engineering applications. Genome analysis of this bacterium revealed that a set of genes associated with CNF biosynthesis and regulation were present in this bacterium, which were also conserved in another six representative Komagataeibacter species having complete genome information. To better understand the metabolic characteristics of K. xylinus DSM 2325, KxyMBEL1810 was reconstructed using genome annotation data, relevant computational resources and experimental growth data generated in this study. Random sampling and correlation analysis of the KxyMBEL1810 predicted pgi and gnd genes as novel overexpression targets for the enhanced CNF production. Among engineered K. xylinus strains individually overexpressing heterologous pgi and gnd genes, either from Escherichia coli or Corynebacterium glutamicum, batch fermentation of a strain overexpressing the E. coli pgi gene produced 3.15 g/L of CNF in a complex medium containing glucose, which was the best CNF concentration achieved in this study, and 115.8% higher than that (1.46 g/L) obtained from the control strain. Genome sequence data and KxyMBEL1810 generated in this study should be useful resources for metabolic engineering of K. xylinus for the enhanced CNF production.

The Effect of Temperament on the Association Between Pre-treatment Anxiety and Chemotherapy-Related Symptoms in Patients With Breast Cancer.

OBJECTIVE: Pre-treatment anxiety (PA) before chemotherapy increases complaints of chemotherapy-related symptoms (CRS). The results on the association have been inconsistent, and the effect of temperament remains unclear. We aimed to determine whether PA is a risk factor for CRS and the effect of differing temperaments on CRS. METHODS: This prospective study comprised 176 breast cancer patients awaiting adjuvant chemotherapy post-surgery. We assessed CRS, PA, and temperament using the MD Anderson Symptom Inventory (MDASI), the Hospital Anxiety and Depression Scale, and the short form of the Temperament and Character Inventory-Revised, respectively. The MDASI was re-administered three weeks after the first chemo-cycle. RESULTS: PA showed weak positive correlation with several CRS after the first cycle; no CRS was significantly associated with PA when pre-treatment depressive symptoms and baseline CRS were adjusted in multiple regression analysis. Moderation model analysis indicated that the PA effect on several CRS, including pain, insomnia, anorexia, dry mouth, and vomiting, was moderated by harm avoidance (HA) but not by other temperament dimensions. In particular, PA was positively associated with CRS in patients with low HA. CONCLUSION: The results in patients with low HA indicate that more attention to PA in patients with confident and optimistic temperaments is necessary.

Metabolic engineering of Escherichia coli for the production of polylactic acid and its copolymers.

Polylactic acid (PLA) is a promising biomass-derived polymer, but is currently synthesized by a two-step process: fermentative production of lactic acid followed by chemical polymerization. Here we report production of PLA homopolymer and its copolymer, poly(3-hydroxybutyrate-co-lactate), P(3HB-co-LA), by direct fermentation of metabolically engineered Escherichia coli. As shown in an accompanying paper, introduction of the heterologous metabolic pathways involving engineered propionate CoA-transferase and polyhydroxyalkanoate (PHA) synthase for the efficient generation of lactyl-CoA and incorporation of lactyl-CoA into the polymer, respectively, allowed synthesis of PLA and P(3HB-co-LA) in E. coli, but at relatively low efficiency. In this study, the metabolic pathways of E. coli were further engineered by knocking out the ackA, ppc, and adhE genes and by replacing the promoters of the ldhA and acs genes with the trc promoter based on in silico genome-scale metabolic flux analysis in addition to rational approach. Using this engineered strain, PLA homopolymer could be produced up to 11 wt% from glucose. Also, P(3HB-co-LA) copolymers containing 55-86 mol% lactate could be produced up to 56 wt% from glucose and 3HB. P(3HB-co-LA) copolymers containing up to 70 mol% lactate could be produced to 46 wt% from glucose alone by introducing the Cupriavidus necator beta-ketothiolase and acetoacetyl-CoA reductase genes. Thus, the strategy of combined metabolic engineering and enzyme engineering allowed efficient bio-based one-step production of PLA and its copolymers. This strategy should be generally useful for developing other engineered organisms capable of producing various unnatural polymers by direct fermentation from renewable resources.

Enhanced Production of Bacterial Cellulose in Komagataeibacter xylinus Via Tuning of Biosynthesis Genes with Synthetic RBS.

Bacterial cellulose (BC) has outstanding physical and chemical properties, including high crystallinity, moisture retention, and tensile strength. Currently, the major producer of BC is Komagataeibacter xylinus. However, due to limited tools of expression, this host is difficult to engineer metabolically to improve BC productivity. In this study, a regulated expression system for K. xylinus with synthetic ribosome binding site (RBS) was developed and used to engineer a BC biosynthesis pathway. A synthetic RBS library was constructed using green fluorescent protein (GFP) as a reporter, and three synthetic RBSs (R4, R15, and R6) with different strengths were successfully isolated by fluorescence-activated cell sorting (FACS). Using synthetic RBS, we optimized the expression of three homologous genes responsible for BC production, pgm, galU, and ndp, and thereby greatly increased it under both static and shaking culture conditions. The final titer of BC under static and shaking conditions was 5.28 and 3.67 g/l, respectively. Our findings demonstrate that reinforced metabolic flux towards BC through quantitative gene expression represents a practical strategy for the improvement of BC productivity.

Quality of Life in Patients with Papillary Thyroid Microcarcinoma Managed by Active Surveillance or Lobectomy: A Cross-Sectional Study.

Background: Active surveillance (AS) is recommended as an alternative to immediate surgery in patients with papillary thyroid microcarcinoma (PTMC), but the impact of AS on quality of life has not been reported. The aim of this study was to compare quality-of-life parameters in patients with PTMC under AS versus those who underwent lobectomy (LB). Methods: In this cross-sectional study, patients with PTMC were prospectively enrolled between June 2016 and October 2017. All patients completed three questionnaires: the 12-item short-form health survey, thyroid cancer-specific quality of life, and fear of progression. The results were compared after adjusting for age, sex, and serum thyrotropin levels. Results: The AS group comprised 43 patients, and the LB group comprised 148 patients. According to the 12-item short-form health survey questionnaire, the score for role limitations due to emotional problems showed a significant negative association between the groups (coefficient [coef]: -7.71 [confidence interval (CI) -15.26 to -0.16], p = 0.045). The thyroid cancer-specific quality of life questionnaire also showed statistically significant differences between the groups with respect to three scores: neuromuscular problems (coef: 4.99 [CI 0.63-10.62], p = 0.020), throat/mouth problems (coef: 5.28 [CI 0.18-10.38], p = 0.043), and scar problems (coef: 9.34 [CI 4.38-14.29], p < 0.001), suggesting a higher level of complaint in the LB group than in the AS group. No significant differences in fear of progression scores were seen between the two groups. Conclusions: Patients with PTMC underwent LB experienced more health-related problems than those managed by AS. These findings support the role of AS as a reasonable management option for patients with PTMC.

A mesoporous carbon-supported Pt nanocatalyst for the conversion of lignocellulose to sugar alcohols.

The conversion of lignocellulose is a crucial topic in the renewable and sustainable chemical industry. However, cellulose from lignocellulose is not soluble in polar solvents, and is, therefore, difficult to convert into value-added chemicals. A strategy to overcome this drawback is the use of mesoporous carbon, which enhances the affinity between the cellulose and the catalyst through its abundant functional groups and large uniform pores. Herein, we report on the preparation of a Pt catalyst supported on a type of 3D mesoporous carbon inspired by Echinometra mathae (Pt/CNE) to enhance the interaction between the catalyst and a nonsoluble reactant. In the hydrolytic hydrogenation of cellulose, the abundant oxygen groups of CNE facilitated the access of cellulose to the surface of the catalyst, and the open pore structure permits cello-oligomers to effectively diffuse to the active sites inside the pore. The highly dispersed Pt performed dual roles: hydrolysis by in situ generating protons from H2 or water as well as effective hydrogenation. The use of the Pt/CNE catalyst resulted in an approximately 80 % yield of hexitol, the best performance reported to date. In direct conversion of hardwood powder, the Pt/CNE shows good performance in the production of sugar alcohols (23 % yield). We expect that the open-structured 3D carbon will be widely applied to the conversion of various lignocellulosic materials.