ason Boudville writes in Science Network Western Australia that Murdoch University School of Veterinary and Life Sciences Algae R&D Centre researcher Dr. Navid Moheimani and his team, in collaboration with the University of Tsukuba, in Japan, have been investigating a non-destructive approach allowing the oil-rich algae Botryococcus braunii to be “milked,” and “re-milked” every five days.
By using the compatible solvent n-heptane, they were able to extract oil from non-growing state algae repeatedly – producing significantly more hydrocarbon and requiring significantly less expensive nutrients, as opposed to the rapid growth phase.
Dr. Moheimani said that B. braunii could replace its external hydrocarbon after five days (after milking) in cultures with one per cent CO2 addition. “The overall external hydrocarbon productivity using non-destructive extraction was at least 20 per cent higher compared with B. braunii grown in conventional semi-continuous culture,” he said.
The efficiency comes from having not to regrow the algae after each extraction, saving on fertilizer usage and waste biomass disposal costs. “So far we have shown that at least two species of Botryococcus braunii can be milked,” he said. “We have also found that at least of one of these species can repeatedly be milked for over 70 days.”
No extra fertilizers were added while cells were being repeatedly milked during that period of time. “It should be noted that, when B. braunii was grown semi-continuously (the conventional method), the total lipid was over 52 per cent higher than the external hydrocarbon extracted by milking,” Dr. Moheimani said.
This new method is compared to conventional biofuel production requiring large quantities of fertilizers followed by harvesting, dewatering, and conversion of wet biomass to the required biofuel at a 30 per cent dry biomass to oil.
Dr. Moheimani and the research team are currently working with Professor Bahri and Dr. de Boer from the School of Engineering at Murdoch University on a potential continuous milking bioreactor reactor.