Growth Aspects and Biochemical Composition of Synechococcus sp. MK568070 Cultured in Oil Refinery Wastewater

Maria Blažina,Ines Haberle,Enis Hrustić,Lucija Konjević,Sunčana Geček,Tina Šilović,Ines Petrić,Andrea Budiša,Tamara Djakovac

doi:10.3390/jmse7060164

Maria Blažina, Ines Haberle + Show 7 more

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https://doi.org/10.3390/jmse7060164

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Abstract

The aim of the study was to explore the possibility of bioremediation of oil refinery wastewaters by the cyanobacterium Synechococcus sp. MK568070, isolated from the Adriatic Sea. The potential of biomass and lipid production was explored upon cultivation on oil refinery wastewater with excess CO2 after the removal of nutrients. The strain grew well in a wide range of salinities and ammonium concentrations, and was further tested on the wastewater from local oil refinery plant of various N-composition. Growth experiment under optimized conditions was used to analyze the lipid, carbohydrate and protein dynamics. The biomass yield was highly dependent on nutrient source and concentration, salinity and CO2 addition. Highest biomass yield was 767 mg/L of dry weight. Towards the end of the experiment the decline in carbohydrate to 18.9% is visible, whereas at the same point lipids, in particular saturated fatty acid methyl esters (FAME), started to accumulate within the cells. The content of lipids at the end of the experiment was 21.4%, with the unsaturation index 0.45 providing good biofuel feedstock characteristics. Fourier Transform Infrared (FTIR) spectroscopy analysis demonstrated a high degree of lipid accumulation in respect to proteins, along with the structural changes and biomass accumulation. In addition, the N-removal from the wastewater was >99% efficient. The potential of lipid accumulation, due to the functional photosynthesis even at the minimal cell quota of nutrients, is critical for the usage of excess industrial CO2 and its industrial transformation to biodiesel. These findings enable further considerations of Synechococcus sp. (MK568070) for the industrial scale biomass production and wastewater remediation.

Highlights

Microalgae have recently drawn a lot of attention as promising candidates for CO2 neutral biofuel production
Most of the efforts studying bioremediation of wastewaters by microalgae are focused on freshwater species, and a substantial part of strains capable of growing under saline conditions needs jet to be explored
The results of this study have demonstrated that Synechococcus sp. (MK568070), a cyanobacterium isolated from Adriatic coastal waters grows on industrial wastewater rich in ammonium, mercaptans, hydrocarbons and other potentially growth-inhibiting substances

Summary

Introduction

Microalgae have recently drawn a lot of attention as promising candidates for CO2 neutral biofuel production. Efforts to overcome problematic economical aspects of the biofuel production from microalgae are directed towards (i) the increase in biomass yield and cellular lipid content by transgenic engineering [2], (ii) optimization of cogeneration process including the use of the excess heat, water and flue gases from the industry and (iii) usage of the effluent water after phycoremediation [3] in agriculture and other purposes. Some selected wild strains of microalgae can naturally produce a high proportion of valuable products such as lipids, carbohydrates or proteins, whereas recent advances in genetic engineering opened the possibilities to produce an even greater variety of valuable molecules useful for food, chemical and pharmaceutical industries [1,2]. Mass production of indigenous microalgae avoids the possible risks associated with large-scale propagation of genetically modified microorganisms and legal constraints related to their use [6]

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