Transforming South Africa’s biodiversity into diesel

Abstract

The continuous use of fossil fuels is environmentally harmful and unsustainable. Concerns about energy supply, environmental pollution and global warming have triggered the worldwide search for sources of environmentally friendly renewable energy. Global biodiesel production and research are focused on crop-based feedstocks, which could become unsustainable in the long term due to arable land and water requirements leading to competition with food crops. Algae have been identified as a second-generation biodiesel feedstock and have the potential to supplement fossil fuels with negligible impact on food security. Microalgae have an oil yield at least 10 times better than oil seed crops and are capable of using environmental waste substrates such as CO2 and nitrate-rich waste water for growth and lipid production. South Africa is among the 17 mega-biodiverse countries in the world. This, coupled with the moderate climate and availability of sunlight, makes South Africa an ideal place to bioprospect for high-lipid-producing algal isolates and the subsequent production of algal biodiesel. The algal team at CSIR Biosciences has been actively sampling South Africa’s biodiversity for the past three years and has successfully obtained over 200 isolates. Various different methodologies related to the isolation of these valuable algae from environmental samples have been used to develop a comprehensive screening and isolation protocol. This protocol includes flow cytometry as a tool for isolation. The protocol was validated and the isolation of 115 micro algal isolates conducted. The isolated samples were further screened for lipid production using a qualitative microscopic assay which rapidly identified high-lipid-producing isolates. Four of the best isolates were selected to be assessed at the secondary level. The secondary evaluation of lipid production required a rapid, semi-quantitative lipid assay, which was developed to equate lipid-related fluorescence with actual lipid content. The lipid production profiles of these isolates ranged from a minimum of 0.4 pg cell to a maximum of 90 pg/cell and the growth rates ranged from 0.52 to 0.13 day-1. Preliminary results demonstrated that there is significant potential to increase lipid production through nutrient stress, and further physiological stresses need to be investigated. The research on developing a process to optimise lipid productivity on a larger scale is still ongoing.