Biological conversion of fuel synthesis process water to single cell protein for aquaculture feed using purple phototrophic bacteria

Qatar has limited freshwater resources and arable land. As a result, fisheries have long played an important role in sustaining the nutritional requirements of Qatar’s population. Under Qatar’s rapid industrial and population development over the last two decades, and those of its neighbours, local fisheries in the Arabian Gulf have come under pressure. This has led to the development of an emerging aquaculture industry within the country. A key requirement for aquaculture is a readily available and sustainably sourced protein rich feed. Traditional sources such as fishmeal are not seen as sustainable, particularly if locally obtained, while plant based alternatives such as soy-meal are also not suitable for local cultivation. Recently, purple non-sulfur bacteria (PNSB), a group of purple-pigmented photosynthetic microorganisms, have been demonstrated as effective sources of single-cell protein, providing increased growth, survival and prevention of disease in various fish and shrimp studies. Like all bacteria, they provide the advantage of rapid cultivation compared to other protein sources and have the benefit of easy selection and enrichment under illuminated anaerobic conditions rich in organic substrate. The use of wastewaters as a substrate is a sustainable approach to cultivate PNSB and other microbial sources of single-cell protein while simultaneously providing environmental protection. However, municipal and agro-industrial wastewaters are typically contaminated with pathogens, inert solids, antibiotics and growth hormones that can impact PNSB culture or pose a threat to aquaculture operations if not effectively separated from the PNSB single-cell protein. In this study we aim to utilize fuel synthesis process water, a significant source of water produced by one of Qatar’s key industries that has highly suitable characteristics for PNSB growth and a composition that can allow for a high purity single-cell protein cultivation. Nevertheless, particular strains of PNSB have been shown to be significantly more beneficial to fish and shrimps than others. We will explore the strains that can be enriched under various unsterilized culture conditions on fuel synthesis process water, and study their growth and cell composition. Selected cultures will be converted to dry fish feed and tested on shrimp and finfish to assess the feed performance on growth and health of the aquatic organisms. Bioreactor design will be optimized based on in-depth culture conditions such as illumination, pH, temperature, and substrate feeding leading to the development of a small-scale pilot system to produce the desired PNSB enrichment. A techno-economic and environmental analysis will be undertaken to evaluate the suitability of this locally produced single-cell protein feed from a circular economy based approach, with the goal of the project to demonstrate the sustainable and safe production of a high-quality local aquaculture feed.

Hamad Bin Khalifa University (HBKU)