Palmeiro-Sanchez, T., Fra-Vazquez, A., Rey-Martinez, N., Campos, J. L., & Mosquera-Corral, A. (2016). Transient concentrations of NaCl affect the PHA accumulation in mixed microbial culture. J. Hazard. Mater., 306, 332–339.
Abstract: The present study explores the feasibility of the accumulation of polyhydroxyalkanoates (PHAs) under the presence of transient concentrations of added sodium chloride, by means of a mixed microbial culture (MMC). This culture was enriched on a mixture of volatile fatty acids (VFAs) containing 0.8 g Na+/L, as NaOH. This MMC presented a maximum PHA accumulation capacity of 53 wt% with 27 Cmol% HV. Accumulation experiments performed with added NaCI at concentrations of 7, 13 and 20 g/L shown that this salt provoked a decrease of the biomass PHA production rate, with an IC50 value close to 7 g NaCl/L. The accumulated PHA was lower than the corresponding value of the assay without the addition of salt. Furthermore, the composition of the biopolymer, in terms of HB:HV ratio, changed from 2.71 to 6.37 Cmol/Cmol, which means a HV decrease between 27 and 14 Cmol%. Summarizing, the PHA accumulation by a MMC non-adapted to saline conditions affected the polymer composition and lead to lower production yields and rates than in absence of added NaCl. (C) 2015 Elsevier B.V. All rights reserved.
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Palmeiro-Sanchez, T., del Rio, A. V., Fra-Vazquez, A., Campos, J. L., & Mosquera-Corral, A. (2019). High -Yield Synthesis of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Copolymers in a Mixed Microbial Culture: Effect of Substrate Switching and F/M Ratio. Ind. Eng. Chem. Res., 58(48), 21921–21926.
Abstract: The accumulation capacity of a mixed microbial culture (MMC) is affected if the substrate used in the accumulation experiments differs from the one used in the enrichment. For this reason, the effect of substrate switching was studied to determine the versatility of an MMC enriched in a mixture of volatile fatty acids (VFA(max)) to overcome this problem. The MMC was enriched using a VFA(max) composed of 48.3:24.3:7.3:14.7 CmM acetic (HAc), propionic (HPr), butyric (HBu), and valeric (HVa) acids, respectively. The accumulation capacity was tested using single VFAs (HAc, HPr, HBu, and HVa), as well as the VFA,Um used in the enrichment. The accumulation capacities were 52.8 +/- 4.7, 48.8 +/- 4.3, 45.2 3.0, 48.4 +/- 1.0, and 54.5 +/- 8.0 wt% for HAc, HPr, HBu, HVa, and rVFA(max) espectively, with polymer compositions of 50.6 15.1, 0.4 0.1, 63.2 1.5, 0.3 0.0, and 2.0 0.7 g 3-HB/g 3-14V, following the same order. The average yields were 0.84 0.08, 0.76 +/- 0.09, 0.74 0.02, 0.70 +/- 0.01, and 0.68 +/- 0.09 CmolpHA/CmolvF, for HVa, VFAmX, HAc, HBu, and HPr, respectively. The feed -to -microorganism (F/M) ratio showed that values of 1-7 CmolvFA/(Cmolx) in the accumulation experiments led to the optimal yields. Based on the results obtained, it seems feasible to enrich an MMC able to produce tailormade biopolymers from different VFAs at high yields.
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Palmeiro-Sanchez, T., Campos, J. L., & Mosquera-Corral, A. (2021). Bioconversion of Organic Pollutants in Fish-Canning Wastewater into Volatile Fatty Acids and Polyhydroxyalkanoate. Int. J. Environ. Res. Public Health, 18(19), 10176.
Abstract: The wastewater from the cookers of a tuna-canning plant was used as feedstock for the process. It was acidified in a continuous stirred tank reactor (CSTR) of 1.5 L to produce a mixture of volatile fatty acids (VFAs). The effluent contained 28.3 & PLUSMN; 8.7 g CODS/L and 25.0 & PLUSMN; 4.6 g CODVFA/L, 4.4 & PLUSMN; 1.6 g NH4+/L, and 10.9 & PLUSMN; 4.0 g Na+/L, which corresponds to about 28 g NaCl/L approximately. This was used to feed a PHA production system. The enriched MMC presented a capacity to accumulate PHAs from the fermented tuna wastewater. The maximum PHA content of the biomass in the fed-batch (8.35 wt% PHA) seemed very low, possibly due to the variable salinity (from 2.2 up to 12.3 g NaCl/L) and the presence of ammonium (which promoted the biomass growth). The batch assay showed a PHA accumulation of 5.70 wt% PHA, but this is a much better result if the productivity of the reactor is taken into account. The fed-batch reactor had a productivity of 10.3 mg PHA/(L h), while the batch value was about five times higher (55.4 mg PHA/(L h)). At the sight of the results, it can be seen that the acidification of fish-canning wastewater is possible even at high saline concentrations (27.7 g NaCl/L). On the other hand, the enrichment and accumulation results show us promising news and which direction has to be followed: PHAs can be obtained from challenging substrates, and the feeding mode during the accumulation stage has an important role to play when it comes to inhibition.
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