ABSTRACT
2-Hydroxybutyric acid (2-HBA) is an important intermediate for synthesizing biodegradable materials and various medicines. Chemically synthesized racemized 2-HBA requires deracemization to obtain optically pure enantiomers for industrial application. In this study, we designed a cascade biosynthesis system in Escherichia coli BL21 by coexpressing L-threonine deaminase (TD), NAD-dependent L-lactate dehydrogenase (LDH) and formate dehydrogenase (FDH) for production of optically pure (S)-2-HBA from bulk chemical L-threonine (L-Thr). To coordinate the production rate and the consumption rate of the intermediate 2-oxobutyric acid in the multi-enzyme cascade catalytic reactions, we explored promoter engineering to regulate the expression levels of TD and FDH, and developed a recombinant strain P21285FDH-T7V7827 with a tunable system to achieve a coordinated multi-enzyme expression. The recombinant strain P21285FDH-T7V7827 was able to efficiently produce (S)-2-HBA with the highest titer of 143 g/L and a molar yield of 97% achieved within 16 hours. This titer was approximately 1.83 times than that of the highest yield reported to date, showing great potential for industrial application. Our results indicated that constructing a multi-enzyme-coordinated expression system in a single cell significantly contributed to the biosynthesis of hydroxyl acids.
Subject(s)
Escherichia coli/genetics , Formate Dehydrogenases , Hydroxybutyrates , Threonine DehydrataseABSTRACT
A whole-cell catalyst using Escherichia coli BL21(DE3) as a host, expressing L- threonine dehydratase from Escherichia coli, and co-expressing leucine dehydrogenase from Bacillus cereus and glucose dehydrogenase from Bacillus subtilis for cofactor regeneration, was constructed and used for one-pot production of L-2-aminobutyric acid (L-ABA) and D- gluconic acid from L-threonine and D-glucose. We used shake-flask culture to study the whole-cell catalytic condition including temperature, pH, proper permeabilization of cells and optimal wet cells amount. Moreover, the whole-cell catalyst was cultured in 5-L fermentor by fed-batch fermentation, and 164 g/L L-threonine and 248 g/L D-glucose were converted to 141.6 g/L L-ABA and 269.4 g/L D-gluconic acid. The whole-cell catalyst is promising to fulfill industrial requirements for L-ABA and D-gluconic acid.
ABSTRACT
<p><b>OBJECTIVE</b>To study the influence of the sequence of three-dimensional conformal radiotherapy (3DCRT) and transcatheter arterial chemoembolization (TACE) on the efficacy and toxicity of treatment in patients with hepatocellular carcinoma (HCC) with portal vein tumor thrombus (PVTT).</p><p><b>METHODS</b>A total of 65 patients who were diagnosed with primary HCC with PVTT were enrolled in the study from November 2008 to March 2012 and were randomly divided into the following two groups:group A,32 patients treated with 3DCRT followed by TACE; group B,33 patients treated with TACE followed by 3DCRT.</p><p><b>RESULTS</b>The total efficacy rates of groups A and B were 68.8% and 69.7% (x² =0.232, P < 0.793). The survival rates,effective percentage of PVTT and AFP remission rates were not significantly different between group A and group B.The exacerbation rate of liver function was significantly higher for group B than for group A (P < 0.05). No serious complication was found in the follow-up period for either group.</p><p><b>CONCLUSION</b>The combination of 3DCRT and TACE is a relatively effective local treatment for patients with primary HCC and PVTT.Compared with TACE followed by 3DCRT, 3DCRT followed by TACE may have a negative influence on liver function.</p>
Subject(s)
Humans , Arteries , Carcinoma, Hepatocellular , Chemoembolization, Therapeutic , Combined Modality Therapy , Liver Neoplasms , Portal Vein , Radiotherapy, Conformal , Survival Rate , Thrombosis , Treatment OutcomeABSTRACT
Objective To observe the efficacy and adverse effects of conventionally fractionated (CF) versus hypofractionated (HF) three-dimensional conformal radiotherapy (3DCRT) for hepatocellular carcinoma (HCC) with portal vein tumor thrombosis.Methods A retrospective analysis was performed on the clinical data of 65 patients with HCC suitable for 3DCRT from 2008 to 2012.These patients were randomly divided into HF group (n =32) and CF group (n =32).The HF group received 3DCRT at a total dose of 45-55 Gy (3-4 Gy/fraction,3-5 fractions/week),while the CF group at a total dose of 40-56 Gy (2 Gy/fraction,5 fractions/week).Results The follow-up rate was 100％.For the HF group and CF group,the short-term response rates were 72％ vs.55％ (P =0.034),the 1-year local control rates were 72％ vs.55％ (P=0.034),the 1-year overall survival rates were 59％ vs.45％ (P=0.042),and the numbers of individuals with grade 1-2 acute gastrointestinal reactions,deterioration of liver function,and radiation hepatitis were 14 vs.11,8 vs.8,and 1 vs.0,respectively (P =0.237).Conclusions HF 3DCRT is superior to CF 3DCRT in the treatment of HCC.
ABSTRACT
Objective:To observe the expression of ATPase F1? in colorectal cancer(CRC) tissues and in LoVo cells,and to discuss its clinical significance.Methods:Expression of ATPase F1? protein in 44 CRC specimens and their adjacent normal tissues(August 2007 to December 2007,Changhai Hospital) and ATPase F1? mRNA in 8 colorectal cancer tissues and their adjacent normal tissues were examined by immunohistochemistry EnVision assay and RT-PCR,respectively.Expression of ATPase F1? on the cell surface of LoVo cells was observed by immunofluorescence.The inhibitory effect of anti-ATPase F1? antibody on the proliferation of LoVo cells was evaluated by CCK-8 assay.Results:Expression of ATPase F1? in the 44 CRCs were significantly higher than those in the adjacent normal tissues as detected by immunohistochemistry(P0.05).Expression of ATPase F1? was observed on the cell surface of LoVo cells,and anti-ATPase F1? antibody significantly inhibited the proliferation of LoVo cells(P