Lipid-rich microalgae are a potential source for the bio-oil production. We isolated a novel oleaginous Thraustochytrid microalga from seawater, Schizochytrium sp. ABC101, and tested the effect of different growth conditions on its production of lipids. Batch fermentation experiments indicated that depletion of nitrogen led to lipid accumulation, and lipid accumulation led to increased cell size and decreased cell wall thickness. Based on these results, we tested three types of fed-batch fermentations (carbon and no nitrogen feeding, carbon and limited nitrogen feeding, carbon and sufficient nitrogen feeding) to examine the effect of adjusting the nitrogen supply on lipid accumulation. The limited nitrogen feeding provided the most efficient lipid production, with maxima after 60 h (dry cell weight [DCW]: 64.7 g/L, lipids: 25.4 g/L, docosahexaenoic acid [DHA]: 11.0 g/L). Use of corn steep liquor (CSL) as the sole nitrogen source also led to excellent performance, with maxima at 84 h (DCW: 86.0 g/L, lipids: 37.2 g/L, DHA: 16.7 g/L). In addition, use of CSL rather than yeast extract reduced the lipid production cost by 50%. Our results suggest that regulation of the nitrogen source improves the efficiency of microalgal lipid production and use of a low-cost nitrogen source reduces production costs. (C) 2020 Published by Elsevier Ltd.