Hello Markad, please clarify your question so your colleagues know where the difficulty is. I understand that you are quite specific about production of organic acids and I think I already addressed that. "Suitable condition" could imply suitable nutritional, environmental or process conditions. Suitability of any of these conditions is peculiar to the target product. Optimal conditions for organic acid production cannot be the same as those for enzymes because conditions for primary metabolism and those for secondary metabolism are different. Whatever condition you refer to has to be obtained by rigorous SCREENING experiments. Let Aspergillus niger select its suitable conditions for organic acid production in solid state fermentation BY ITSELF.