A method for increasing the lipid content of algae includes combining algae and a lipid-precipitating addition in a growth-inhibitive medium, the growth-inhibitive medium being deficient in at least one nutrient that is necessary for reproductive growth of algae, thus frustrating algae reproduction, the lipid-precipitating addition selected from hydroxyl-containing compounds and amine-containing compounds. An organic acid addition may also be combined with the lipid-precipitating addition and algae in the growth-inhibitive medium, the organic acid addition including compounds containing carboxylic acid functionality. Direct production of biodiesel is also achieved by the use of particular lipid-precipitating additions and organic acid additions.