MOLECULAR IDENTIFICATION OF FUNGI ASSOCIATED WITH DECOMPOSITION OF DOMESTIC FOOD WASTES

Abstract

The aim of this study was to determine the loads, types, molecular identities and genetic relatedness of fungi associated with the decomposition of Domestic Food Wastes (DFW) from Akure Metropolis in Nigeria. The DFW collected from different locations were peels of cassava, cocoyam, pawpaw, orange, banana, yam, ripe and unripe plantain, pineapple, pulps of pawpaw and orange and vegetables (Solanecio biafrae, Amaranthus hybridus and African spinach). They were mixed with poultry droppings in a ratio of 3:1 and decomposed naturally at 28oC + 2oC for eight weeks. Fungi from the various and combined wastes were isolated, enumerated and identified at one wk intervals using conventional microbiological methods. Molecular identities and genetic relatedness of the isolates were investigated using standard molecular techniques. Before DFW decomposition, the highest and the lowest fungal loads (3.5 x 105 sfu/g and 1.0 x 106 sfu/g) were obtained in waste cooked rice and Solanecio biafrae; and cocoyam peels. The highest and the lowest fungal loads were 3.0 x 106 sfu/g and 2.5 x 105 sfu/g on the respective 3rd and 2nd weeks of decomposition. The species identified were Rhizopus stolonifer WXM171, R. stolonifer lipRs, Saccharomyces cerevisiae LA28, S. cerevisiae 8F13, Candida albicans CAU40704.1, C. albicans SC5314, C. dublinensis CD36, C. tropicalis RB60, Geotrichum candidum ATCC, Aspergillus niger 1ST101, A. niger A156 and A. niger SMS03, A. flavus adh1, A. flavus NRRL3357, A. flavus C124, A. alabamensis DTO15F9, A. terreus AKF2, A. terreus BSD, A. tubingensis 0932, A. fumigatus LCF20, A. fumigatus 015FIT, Penicillium citrinum ESF2M, P. citrinum NZDmf108, P. citreonigrum FRR2046, P. citreonigrum DTO128H4, Trichoderma reesei QM6a, M. mucedo ARD25Y3, Fusarium oxysporium f.sp vasinfectum, F. oxysporium f.sp lycopersici and Neurospora crassa M1991 using molecular techniques. The same genera were identified using the traditional method except for M. mucedo and T. reesei. Both fungi were misnamed as R. stolonifer and A. flavus respectively. Also, some fungal species and all the strain names were not revealed. Some of the identified fungi were genetically related to one another while some had distant relationship and others were not related. The two identified strains of R. stolonifer had the highest (sum) level of occurrence (50%) before and during DFW decomposition. Each of the strain of G. candidum, A. fumigatus, F. oxysporium, C. dublinensis, P. citreonigrum and P. citrinum had the lowest occurrence of 7% respectively. Candida. albicans, S. cerevisiae and R. stolonifer and Aspergillus spp. occurred at the early weeks (0-3 weeks) of decomposition, while P. citreonigrum, R. stolonifer, M. mucedo and T. reesei are found at the middle weeks (4-6 weeks) to succeed the earlier fungi and Fusarium. oxysporium, Aspergillus spp., G. candidum, C. albicans and R. stolonifer dominated the latter weeks (7-8 weeks) of decomposition. This study has thrown more light on the correct identities, genetic relationships and occurrence of the fungi associated with the decomposition of DFW. This information serves as a basis to acquire more knowledge about the roles of the fungi in the DFW decomposition and hence useful for the control of environmental pollution and adverse human health effects often associated with the wastes.