Acinetobacter radioresistens PR8 produces extracellular lipase depending upon growth media. In present work we not only screened the nutrient sources but also investigated the causes for variation in productivity. The nutrient sources investigated are, groundnut oil, groundnut cake and fresh groundnut. Lower lipase productivity was observed on fresh ground nut in contrast to groundnut oil and groundnut cake. The lipase productivity was examined in the batch and parameters monitored were bacterial growth, enzyme activity, pH, lipids and protein concentration. The aflatoxin B1 and oxalic acid present in fresh groundnut were found to be responsible for lower lipase productivity. The interaction studies of oxalic add and purified lipase was confirmed with CD spectra analysis, isothermal titration calorimetry studies and fluorescence quenching. Therefore, the importance of economical cheap groundnut cake with no aflatoxin B1 and oxalates are proposed to be used for optimum lipase production. (C) 2017, The Society for Biotechnology, Japan. All rights reserved.