Potential for Biomass Production and Remediation by Cultivation of the Marine Model Diatom Phaeodactylum tricornutum in Oil Field Produced Wastewater Media

Abstract

While oilfield produced water (PW) is one of the largest, unclaimed wastewater streams of the oil industry, it could potentially be used as a cultivation medium for microalgae. Microalgae could help with the remediation of this water while also delivering biomass that can be transformed into valuable byproducts such as biofuels. The coupling of these two purposes is expected to cut production costs of biofuels while aiding environmental protection. In this study, we compared the cultivation capacity of the marine model diatom Phaeodactylum tricornutum in media at varying salinities and in media composed of PW from two oilfields in the Central Valley of California that differed drastically in the concentration of inorganic and organic constituents. Specifically, we measured the carrying capacity of these media, the maximum growth rates of P. tricornutum, its cellular lipid accumulation capacity, and its capacity to remediate the most polluted PW source. Our study shows that P. tricornutum can successfully adjust to the tested cultivation media through processes of short-term acclimation and long-term adaptation. Furthermore, the cultivation of P. tricornutum in the most heavily polluted PW source led to significant increases in cell yield and improved photosynthetic capacity during the stationary phase, which could be attributed chiefly to the higher levels of nitrate present in this PW source. Chemical water analyses also demonstrated the capability of P. tricornutum to remediate major nutrient content and potentially harmful elements like fluorine and copper. Because P. tricornutum is amenable to advanced genetic engineering, which could be taken advantage of to improve its cultivation resilience and productivity in an economic setting, we propose this study as a step towards essential follow-up studies that will identify the genetic regulation behind its growth in oilfield PW media and its remediation of the PW constituents.

A synthetic biology approach for the treatment of pollutants with microalgae

“…Another microalga of interest is P. tricornutum, a marine diatom that is well known for high accumulation of omega-3 fatty acids (up to 35% of cell weight) and enriched protein (Pudney et al, 2019). P. tricornutum has demonstrated rapid growth rates in saline wastewater and is of particular interest for remediation of both inorganic and organic contaminants in oilfield produced water where it has demonstrated 92, 76, 85, 72% and 56% removal of nitrate, phosphate, iron (Fe), fluorine (F), and Mg, respectively (Gillard et al, 2021). P. tricornutum is one of two algal species that have been investigated for transgenic biodegradation of polyethylene terephthalate (PET) plastic (Moog et al, 2019), as it has advanced genetic toolkits available (George et al, 2020).…”

Physiochemical and molecular responses of the diatom Phaeodactylum tricornutum to illumination transitions

“…Phaeodactylum tricornutum , a marine model diatom, has been widely studied in the fields of ecology, biochemistry, molecular biology and biorefinery processes [ 4 , 5 ]. Furthermore, the alga is known to biosynthesize high-value and broad-market compounds, e.g., fucoxanthin, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and is considered as a commercially feasible strain with large-scale production potential [ 1 , 6 , 7 ]. During the process of artificial cultivation, the target compounds in P. tricornutum can be impacted by culture conditions and thus the conditions should be optimized to enhance production.…”

Towards the usage of Phaeodactylum tricornutum as biofactory for omega-3 fatty acids

“…Based on genetic and physiological studies on P. tricornutum strains (Martino et al 2007;Martino et al 2011;Rastogi et al 2020), as discussed in section 1.1, it can very likely be assumed that the salinity tolerance differs between strains, according to their long-term selective pressure. In a long-term adaption experiment with Pt4 (CCAP 1052/6) and Pt1(CCAP 1052/1) these findings could not be supported (Gillard et al 2021). In another study with Pt4 (UTEX 646) maximum biomass and lipid content were achieved at a salinity of 20% within the growth medium, while EPA content was highest at lowest salinity (5%) (Wang et al 2018).…”