BACKGROUND: Vanillic acid is a flavoring agent and also serves as precursor for vanillin production. Culture medium and fermentation condition for the single step production of vanillic acid from Phanerochaete chrysosporium using lignocellulosic waste as a substrate under solid state fermentation (SSF) were optimized using response surface methodology. RESULTS: The process parameters were chosen by borrowing methodology, and L-asparagine, pH and moisture content of the solid medium during SSF were identified as the most significant variables. The optimum value of selected variable and their mutual interactions were determined by response surface methodology. The result demonstrated that a yield of 73.58 mg vanillic acid g(-1) substate was predicted under optimum conditions (L-asparagine 5.98 mmol L(-1) (2.37mg g(-1) groundnut shell), pH of solid medium 4.51 and moisture content 74.83%). The predicted response was experimentally validated and resulted in amaximum vanillic acid yield of 73.69 mg g(-1) after 8 days of SSF. CONCLUSION: The optimization of fermentation variables resulted in a maximum 10-fold increase in vanillic acid yield compared with that observed under sub-optimal conditions (from 7.2 mg g(-1) to 73.69 mg g(-1)). (C) 2011 Society of Chemical Industry