Improvement of Pyruvate Production Based on Regulation of Intracellular Redox State in Engineered Escherichia coli

Maohua Yang,Jianmin Xing 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.4

The commercial demand for pyruvate has been expanding. However, some challenges need to be overcome in the microbial production of pyruvate, such as low glucose consumption caused by excessive accumulation of NADH. In this study, weakening or block of the TCA cycle, overexpression of foreign NADH oxidase, and carbon sources with different oxidation state was attempted to decrease NADH accumulation in engineered strain YP211. Results showed that blocking or weakening TCA cycle could not lower the intracellular redox state in strain YP211.Overexpressing NADH oxidase from Lactococcus lactis significantly decreased the intracellular NADH content and increased the consumption rate of glucose. However, the yield of pyruvate did not increase significantly. Compared with glucose as carbon source, sodium gluconate with a higher oxidation state resulted in a significant decrease of NADH/NAD+, and the concentration and yield of pyruvate increased by 62 and 6%, respectively. In the fed-batch fermentation, the yield of pyruvate increased to 0.78 g/g gluconate, and the concentration of pyruvate reached 78.8 g/L. It was suggested that sodium gluconate was a more ideal carbon source for strain YP211, which could effectively decrease NADH content and improve the pyruvate production.

Enhanced Sulfate Reduction by Citrobacter sp. Coated with Fe3O4/SiO2 Magnetic Nanoparticles

Wei Zhou,Maohua Yang,Ziyu Song,Jianmin Xing 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.1

A sulfate-reducing Citrobacter strain was isolatedand coated with Fe3O4/SiO2 magnetic nanoparticles(MNPs) to enhance sulfate reduction. Biolog analysisshowed that it utilizes a broad range of electron donors. The findings also showed that this bacteria strain is afacultative anaerobe and can completely reduce 12 mM ofsulfate to sulfide in 7 days under anaerobic conditions. Moreover, sulfate reduction was enhanced by 79% underoptimized conditions. Different SiO2 wrap-ratios of theMNPs attached to the cell surface were studied to optimizethe sulfate reduction: the surface of cells coated with 300%silica wrap-ratio MNPs showed the highest stability andincreased desulfurization batch time, with a 450% increasein sulfate reduction in comparison with uncoated cellscultivated in anaerobic conditions.

Rate-based model for predicting and evaluating H2S absorption in the haloalkaliphilic biological desulfurization process

Zheng Chen,Gama Yang,Tingzhen Mu,Maohua Yang,Nadia A. Samak,Sumit Peh,Yunpu Jia,Xuemi Hao,Xuhao Zhao,Jianmin Xing 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.110 No.-

The highly efficient performance of H2S absorption is the crucial indicator for haloalkaliphilic biologicaldesulfurization (HBDS) because it immediately concerns the H2S removal efficiency and pH change ofalkaline solutions. Therefore, we investigated the effect of operating parameters on the H2S absorption’sperformance under haloalkaline conditions. The gas–liquid ratio and packing height significantly improveH2S removal efficiency, from 80% to 90% and 66% to 99%, respectively. The absorption temperature had atrivial impact on the H2S removal efficiency, and the maximum value appeared at 45 C. Additionally, alloperating parameters caused pH changes that varied in the acceptable range (0.1 to 0.5) during theabsorption process. A rate-based model was successfully developed to predict the haloalkaliphilic H2Sabsorption process accurately. Moreover, this model could be implemented to effectively evaluate theHBDS system’s stability and provide reliable theoretical guidance for the industrial HBDS process toensure good process stability.

Kinetic Evaluation of Products Inhibition to Succinic Acid Producers Escherichia coli NZN111, AFP111, BL21, and Actinobacillus succinogenes 130ZT

Qiang Li,Dan Wang,Yong Wu,Maohua Yang,Wangliang Li,Jianmin Xing,Zhiguo Su 한국미생물학회 2010 The journal of microbiology Vol.48 No.3

Succinic acid is one of the platform compounds and its production via natural feedstocks has drawn worldwide concerns. To evaluate the inhibitory effects of fermentation products on the growth of Actinobacillus succinogenes 130ZT and Escherichia coli NZN111, AFP111, BL21, fermentations with addition of individual products in medium were carried out. The cell growth was inhibited when the concentrations of formate, acetate, lactate, and succinate were at range of 8.8-17.6 g/L, 10-40 g/L, 9-18 g/L, and 10-80 g/L, respectively. For these two species of bacteria, E. coli was more resistant to acid products than A. succinogenes, while both endured succinate rather than by-products. As a result of end product inhibition, succinate production yield by A. succinogenes decreased from 1.11 to 0.49 g/g glucose. Logistic and Monod mathematical models were presented to simulate the inhibition kinetics. The Logistic model was found more suitable for describing the overall synergistic inhibitory effects.

Ribosome-binding Sequences (RBS) Engineering of Key Genes in Escherichia coli for High Production of Fatty Alcohols

Ruonan Chen,Yilan Liu,Wei Zhong,Hao Xuemi,Tingzhen Mu,Maohua Yang,Jianmin Xing 한국생물공학회 2022 Biotechnology and Bioprocess Engineering Vol.27 No.4

Fatty alcohols are widely used in the fields of food, pharmaceutical and renewable energy and so on, thus biosynthesis of fatty alcohols has attracted wide attention in recent years. However, the concentration of fatty alcohols is still at a low level. In this paper, we constructed an Escherichia coli strain with high yield of fatty alcohols through the combinatorial regulation of three key genes of fabH, fabZ, and far. Firstly, we designed new ribosomebinding sequences (RBS) of fabH and fabZ with 10-fold strengths compared to the original ones by RBS calculator, separately. Secondly, we engineered the starting strain MGL1 by replacing the original RBS with designed ones, which resulted in MGLHS (fabH-RBS1), MGLZS (fabZRBS2), and MGLHZS (fabH-RBS1/fabZ-RBS2), respectively. Thirdly, the plasmid pL1 harboring far gene was transferred into above strains to test fatty alcohols production under the induction of different isopropyl-β-D-thiogalactoside concentrations. The results showed that the concentration of fatty alcohols in strains MGLHS-far, MGLZS-far and MGLHZS-far reached 2.75 g/L, 2.54 g/L and 3.82 g/L, respectively, which increased 35%, 25% and 88% than that of the starting strain MGL1-far. The fatty alcohols reached 9.35 g/L in fed batch fermentation with MGLHZS-far, of which the main components were two saturated fatty alcohols (C14:0 and C16:0) and two unsaturated fatty alcohols (C16:1 and C18:1). The results demonstrated that combinatorial regulation of three key genes of fabH, fabZ, and far in E. coli can achieve high-yield production of fatty alcohols.

Unraveling of Enigmatic Hearing-Impaired <i>GJB2</i> Single Heterozygotes by Massive Parallel Sequencing: DFNB1 or Not?

Kim, So Young,Kim, Ah Reum,Kim, Nayoung K. D.,Lee, Chung,Kim, Min Young,Jeon, Eun-Hee,Park, Woong-Yang,Choi, Byung Yoon,Xie., Maohua Williams & Wilkins Co 2016 Medicine Vol.95 No.14

<▼1><P>Supplemental Digital Content is available in the text</P></▼1><▼2><P><B>Abstract</B></P><P>The molecular etiology of nonsyndromic sensorineural hearing loss (SNHL) in subjects with only one detectable autosomal recessive <I>GJB2</I> mutation is unclear. Here, we report <I>GJB2</I> single heterozygotes with various final genetic diagnoses and suggest appropriate diagnostic strategies. A total of 160 subjects with SNHL without phenotypic markers were screened for <I>GJB2</I> mutations. Single-nucleotide variants or structural variations within the DFNB1 locus or in other deafness genes were examined by Sanger sequencing, breakpoint PCR, and targeted exome sequencing (TES) of 129 deafness genes. We identified 27 subjects with two mutations and 10 subjects with only one detectable mutation in <I>GJB2.</I> The detection rate of the single <I>GJB2</I> mutation among the 160 SNHL subjects in the present study (6.25%) was higher than 2.58% in normal hearing controls in Korean. The DFNB1 was clearly excluded as a molecular etiology in four (40%) subjects: other recessive deafness genes (N = 3) accounted for SNHL and the causative gene for the other non-DFNB1 subject (N = 1) was not identified. The etiology of additional two subjects was potentially explained by digenic etiology (N = 2) of <I>GJB2</I> with <I>MITF</I> and <I>GJB3</I>, respectively. The contribution of the single <I>GJB2</I> mutation in the four remaining subjects is unclear. Comprehensive diagnostic testing including TES is prerequisite for understanding <I>GJB2</I> single heterozygotes.</P></▼2>