Palm Oil Mill Effluent for Lipid Production by the Diatom Thalassiosira pseudonana

Karthick Murugan Palanisamy,Mohd Hasbi Ab Rahim,Gaanty Pragas Maniam,Natanamurugaraj Govindan,Ahmad Ziad Sulaiman,Yusuf Chisti

doi:10.3390/fermentation8010023

Karthick Murugan Palanisamy, Mohd Hasbi Ab Rahim + Show 4 more

Open Access

https://doi.org/10.3390/fermentation8010023

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Abstract

Biomass and lipid production by the marine centric diatom Thalassiosira pseudonana were characterized in media based on palm oil mill effluent (POME) as a source of key nutrients. The optimal medium comprised 20% by volume POME, 80 µM Na2SiO3, and 35 g NaCl L−1 in water at pH ~7.7. In 15-day batch cultures (16:8 h/h light–dark cycle; 200 µmol photons m−2 s−1, 26 ± 1 °C) bubbled continuously with air mixed with CO2 (2.5% by vol), the peak concentration of dry biomass was 869 ± 14 mg L−1 corresponding to a productivity of ~58 mg L−1 day−1. The neutral lipid content of the biomass was 46.2 ± 1.1% by dry weight. The main components of the esterified lipids were palmitoleic acid methyl ester (31.6% w/w) and myristic acid methyl ester (16.8% w/w). The final biomass concentration and the lipid content were affected by the light–dark cycle. Continuous (24 h light) illumination at the above-specified irradiance reduced biomass productivity to ~54 mg L−1 day−1 and lipid content to 38.1%.

Highlights

Palm oil is globally the most widely consumed vegetable oil
palm oil mill effluent (POME) can be used as a cheap source of some nutrients in culture media for growing microalgae to produce various possible products, including biomass for aquaculture feed, natural colorants such as astaxanthin, and polyunsaturated fatty acids such as docosahexaenoic acid [4,5]
The isolated diatom (Figure 1) was identified as Thalassiosira pseudonana based on the morphological features (general morphology, valve diameter, number of rimoportulae) seen in field emission scanning electron microscopic images of the cleaned frustules

Summary

Introduction

Palm oil is globally the most widely consumed vegetable oil. Palm oil is produced in tropical regions such as Indonesia, Malaysia, and Thailand. Each metric ton of palm oil produced generates between 2.5 and 3 tons of POME [1,2]. Microalgae, including diatoms, are sources and potential sources of diverse products [3,4,5,6,7] including edible oils. POME can be used as a cheap source of some nutrients in culture media for growing microalgae to produce various possible products, including biomass for aquaculture feed, natural colorants such as astaxanthin, and polyunsaturated fatty acids such as docosahexaenoic acid [4,5]. Absorption of nutrients from POME by microalgae can reduce its polluting potential [5,8,9]. POME-based culture media have supported good growth of diverse microalgae including diatoms such as Chaetoceros affinis [10], Gyrosigma sp. POME cannot be used undiluted in algal culture media because of two factors: the dark color of undiluted POME prevents the algal cells from accessing light [10] and certain compounds naturally present in POME inhibit the growth of algal cells if added in a high concentration [14,15,16]

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