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Investigation of polyhydroxyalkanoates (PHAs) biosynthesis from mixed culture enriched by valerate-dominant

Jiuxiao Hao, Xiujin Wang, Hui Wang

《环境科学与工程前沿（英文）》 2017年第11卷第1期 doi: 10.1007/s11783-017-0896-8

摘要： Valerate-hydrolysate enriched culture showed great ability to produce 3HV and 3H2MV. Valerate-hydrolysate enriched culture had more in the community. Mixed iso-/n-valerate was effective at balancing microbial growth and PHAs synthesis. Co-substrates of valerate and propionate raised the fraction of 3HV and 3H2MV. The production of polyhydroxyalkanoates (PHAs) with a high fraction of 3-hydroxyvalerate (3HV) and 3-hydroxy-2-methylvalerate (3H2MV) from mixed culture enriched by valerate-dominant hydrolysate was evaluated in this study. After long-term enrichment, the culture showed strong ability to synthesize 3HV and 3H2MV, even with acetate-dominant substrate. The ultilization of single or mixed iso-/n-valerate by the enriched culture showed that the mixture of iso-valerate and n-valerate was more efficient substrate than any single in terms of balancing microbial growth and PHAs synthesis. Besides, through comparing the kinetics and stoichiometry of the tests supplying valerate and propionate, the enriched culture with equivalent valerate and propionate (1:1 molar ratio) exhibited superior PHAs production performances to pure valerate or propionate, attaining more than 70 mol% of 3HV and 3H2MV. The above findings reveal that valerate-dominant hydrolysate is a kind of suitable substrate to enrich PHAs producing culture with great capability to synthesize 3HV and 3H2MV monomers, thus improving product properties than pure poly(3-hydroxybutyrate) (P3HB); also 3HV and 3H2MV production behaviors can be regulated by the type of odd-carbon VFAs in the substrate.

关键词： Polyhydroxyalkanoates (PHAs) Valerate Mixed culture 3-hydroxyvalerate (3HV) Propionate

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Research on polyhydroxyalkanoates and glycogen transformations: Key aspects to biologic nitrogen and

Hongjing LI, Yinguang CHEN

《环境科学与工程前沿（英文）》 2011年第5卷第2期页码 283-290 doi: 10.1007/s11783-010-0243-9

摘要： In this paper, a study was conducted on the effect of polyhydroxyalkanoates (PHA) and glycogen transformations on biologic nitrogen and phosphorus removal in low dissolved oxygen (DO) systems. Two laboratory-scale sequencing batch reactors (SBR1 and SBR2) were operating with anaerobic/aerobic (low DO, 0.15–0.45 mg·L ) configurations, which cultured a propionic to acetic acid ratio (molar carbon ratio) of 1.0 and 2.0, respectively. Fewer poly-3-hydroxybutyrate (PHB), total PHA, and glycogen transformations were observed with the increase of propionic/acetic acid, along with more poly-3-hydroxyvalerate (PHV) and poly-3-hydroxy-2-methyvalerate (PH2MV) shifts. The total nitrogen (TN) removal efficiency was 68% and 82% in SBR1 and SBR2, respectively. In the two SBRs, the soluble ortho-phosphate (SOP) removal efficiency was 94% and 99%, and the average sludge polyphosphate (poly-P) content (g·g-MLVSS ) was 8.3% and 10.2%, respectively. Thus, the propionic to acetic acid ratio of the influent greatly influenced the PHA form and quantity, glycogen transformation, and poly-P contained in activated sludge and further determined TN and SOP removal efficiency. Moreover, significant correlations between the SOP removal rate and the (PHV+ PH2MV)/PHA ratio were observed ( >0.99). Accordingly, PHA and glycogen transformations should be taken into account as key components for optimizing anaerobic/aerobic (low DO) biologic nitrogen and phosphorus removal systems.

关键词： low dissolved oxygen (DO) biological nitrogen and phosphorus removal polyhydroxyalkanoates (PHA) glycogen