Abstract
The fishing industry produces vast amounts of saline organic side streams that require adequate treatment and disposal. The bioconversion of saline resources into value-added products, such as biodegradable polyhydroxyalkanoates (PHAs), has not yet been fully explored. This study investigated PHA production by mixed microbial cultures under 30 gNaCl/L, the highest NaCl concentration reported for the acclimatization of a PHA-accumulating mixed microbial culture (MMC). The operational conditions used during the culture-selection stage resulted in an enriched PHA-accumulating culture dominated by the Rhodobacteraceae family (95.2%) and capable of storing PHAs up to 84.1% wt. (volatile suspended solids (VSS) basis) for the highest organic loading rate (OLR) applied (120 Cmmol/(L.d)). This culture presented a higher preference for the consumption of valeric acid (0.23 ± 0.03 CmolHVal/(CmolX.h)), and the 3HV monomer polymerization (0.33 ± 0.04 CmmolHV/(CmmolX.h) was higher as well. As result, a P(3HB-co-3HV)) with high HV content (63% wt.) was produced in the accumulation tests conducted at higher OLRs and with 30 gNaCl/L. A global volumetric PHA productivity of 0.77 gPHA/(L.h) and a specific PHA productivity of 0.21 gPHA/(gX.h) were achieved. These results suggested the significant potential of the bioconversion of saline resources into value-added products, such as PHAs.
Highlights
The fish and seafood segment from the agro-food industry is growing globally with a compound annual growth rate (CAGR) of 4.8% (2021–2026) towards a market value of EUR 518 billion by 2021 [1]
The sequence batch reactor (SBR) was inoculated with sediments collected from a saline area of Rio Tejo (Samouco, Portugal) that were passed through a filtration sieve (350 μm)
In order to select a halotolerant PHA-accumulating mixed microbial culture (MMC), sediments collected from a saline area (Samouco, Portugal) were used to inoculate the SBR with halotolerant organisms and submitted to an solids retention time (SRT) for three days and to an aerobic dynamic feeding, namely the conventional feast and and famine (F/f) regime and the decoupled carbon and nitrogen feeding, throughout the operation
Summary
The fish and seafood segment from the agro-food industry is growing globally with a compound annual growth rate (CAGR) of 4.8% (2021–2026) towards a market value of EUR 518 billion by 2021 [1]. The fishery industry has been associated with high nutritional and commercial value, it has generated a large amount of organic side streams that require adequate treatment and disposal [2,3]. Companies have been required to conduct expensive treatments of those saline streams before they can be safely disposed, as the conventional biological treatments for organic compound removal are less efficient due to their strong salt inhibition [5,6]. The ability to use these saline organic side streams as feedstock for biologic processes would be economically favourable for these industries by reducing treatment costs while reducing the environmental burden caused by the commonly used chemicals during treatment [7]. The conversion of these resources into value-added products, such as polyhydroxyalkanoates (PHAs), would decrease the costs of treatment and contribute towards a circular economy
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