Eco-friendly, economic fungal universal medium from watermelon peel waste

Watermelon peel waste (WPW) is a zero value material containing a high amount of nutrients that could be utilized in microbial growth medium production. In the present work, WPW was used to produce universal fungal growth medium with great nutritional profile to use instead of other expensive media particularly the Potato dextrose agar (PDA) medium. The mechanical and physical pretreatments were used to extract the growth medium from WPW. The main fiber composition was estimated as well as the elemental analysis and energy dispersive X-ray analysis (EDX) for the extracted medium. The total proteins, lipids and reducing sugars content were measured. The extracted WPW medium showed a high value of those macronutrients 9, 0.32 and 11 gl^-1 respectively. The results of this study showed that mechanical pretreatment of WPW is the best for fungal growth; where the dry biomass obtained for Rhizopus oryzae, Lichtheimia corymbifera, Aspergillus niger, Penicillium expansium and Fusarium oxysporum were 1.53, 2.03, 2.37, 2.67 and 3.12 gl^-1 respectively. Taguchi design was used to optimize the medium components. The optimum growth medium composition was prepared as follows; blending 500 gl^-1 fresh WPW and 10 gl^-1 of dextrose. Moreover dry biomass of R. oryzae on three liquid media namely watermelon peel waste dextrose (WPWD), Potato dextrose (PD) and Czapek^,s dox (CzD) were 4.49, 4.16 and 2.39 respectively. Similarly, in the case of L. corymbifera, A. niger and P. expansium the dry biomass was increased on WPWD by 276, 267 and 250% respectively, while the dry biomass of F. oxysporum on WPWD was increased by 199%. Moreover, physicochemical properties of WPWDA medium are similar to PDA and CzDA. The formulated WPWDA medium is an alternative to commonly used media such as PDA and CzDA; and very effective for the growth of fungi, also this medium is eco-friendly and cheap.