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<p>Microbial production of polyhydroxyalkanoates (PHA) remains a significant challenge due to low yields, slow growth rates, and limited PHA accumulation capacities. This study investigated the growth promoters of mixed phototrophic purple bacteria (PPB) for PHA production by cultivating under various conditions. Infra-red (IR) light intensity (10–277 W/m<sup>2</sup>), initial pH (acidic or neutral), and soluble chemical oxygen demand to ammonium ratios (COD/N of 100–10:1) were optimized. The highest concentration of pigments and PHA were achieved at 53 W/m<sup>2</sup> IR intensity. Under these conditions, most of the CO<sub>2</sub> was sequestered by PPB, H<sub>2</sub> production was reduced and PHA production was increased. Neutral pH enhanced bacteriochlorophyll and PHA concentrations and COD removal efficiency compared to acidic conditions. Low COD/N ratios improved PHA-related parameters, including production of polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV), despite reduced NH<sub>4</sub><sup>+</sup> depletion. Under optimum conditions (53 W/m<sup>2</sup>, pH 7.0, COD/N 10:1), 74.70% COD removal and maximum PHA concentration of 968.81 mg/l (PHB:PHV = 91:9) were achieved, with 80.64%gVSS content. The maximum PHA production rate and productivity were 0.566 mg COD<sub>PHA</sub>/mg COD<sub>X</sub>.d and 0.206 mgCOD<sub>PHA</sub>/l.d, respectively. Results indicate PPB’s potential for enhanced PHA accumulation and COD reduction under IR-anaerobic feast conditions while improving bacterial pigment production.</p>

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Efficient Synthesis of Infrared-Driven Polyhydroxyalkanoate and Wastewater Treatment by Mixed Phototrophic Purple Bacteria

  • 期刊论文

  • 发表日期：

    2025年4月28日

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  • Ali Matinfar,
  • Ghasem Najafpour-Darzi,
  • Maedeh Mohammadi,
  • Habibollah Younesi

摘要

Microbial production of polyhydroxyalkanoates (PHA) remains a significant challenge due to low yields, slow growth rates, and limited PHA accumulation capacities. This study investigated the growth promoters of mixed phototrophic purple bacteria (PPB) for PHA production by cultivating under various conditions. Infra-red (IR) light intensity (10–277 W/m2), initial pH (acidic or neutral), and soluble chemical oxygen demand to ammonium ratios (COD/N of 100–10:1) were optimized. The highest concentration of pigments and PHA were achieved at 53 W/m2 IR intensity. Under these conditions, most of the CO2 was sequestered by PPB, H2 production was reduced and PHA production was increased. Neutral pH enhanced bacteriochlorophyll and PHA concentrations and COD removal efficiency compared to acidic conditions. Low COD/N ratios improved PHA-related parameters, including production of polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV), despite reduced NH4+ depletion. Under optimum conditions (53 W/m2, pH 7.0, COD/N 10:1), 74.70% COD removal and maximum PHA concentration of 968.81 mg/l (PHB:PHV = 91:9) were achieved, with 80.64%gVSS content. The maximum PHA production rate and productivity were 0.566 mg CODPHA/mg CODX.d and 0.206 mgCODPHA/l.d, respectively. Results indicate PPB’s potential for enhanced PHA accumulation and COD reduction under IR-anaerobic feast conditions while improving bacterial pigment production.