The Role of Pleurotus Ostreatus Hybrid in Bioconversion of Lignocellulose Waste Materials into Affordable Protein Food in Ghana

Abstract

Pleurotus ostreatus, commonly known as the Black Pearl Oyster mushroom or Shimofuri Hiratake in Japanese language, is a novel species gaining commercial interest in parts of North America and Asia. Recently, this mushroom has been introduced into Ghana for commercial cultivation. This study aimed at domesticating this mushroom in Ghana through a series of experiments. i.e. its growth parameters, substrate optimization, and fruiting potential under controlled conditions. In vitro mycelial vegetative radial growth studies were conducted on Potato Dextrose Agar (PDA) and Malt Extract Agar (MEA). Optimal growth occurred at 28 ± 2 °C and 75% relative humidity, reaching 90 ± 0 mm radial diameter within 7 days. Spawn production trials showed that boiled dark red sorghum grains were colonized in 15 days at either 24 °C or 28 °C, whereas hot water-treated samples took 20 days to cover with the spawn. On the other hand, millet grains were smaller and more compact and irrespective of heat treatment and incubation temperature could not retain moisture leading to lengthening of period of spawn coverage to 22 days. The Molecular analysis of this study confirmed that the Pleurotus variants; Pleurotus ostreatus EM-1 (Pearl Oyster) and P. ostreatus (black pearl oyster) are what we have in Ghana. The Phylogenetic tree of P. ostreatus indicated that P. ostreatus PC15 (Reference) is clearly related to P. ostreatus Black pearl oyster (BKPO). Therefore Black pearl oyster and PC 15 (Reference) are genetically similar. P. ostreatus EM-1 (POM) is on a separate branch from Black pearl oyster and PC 15 showing that it has a genetic divergence but is still relatively close. Black pearl oyster and PC 15 are closely related and share a common ancestor than any of the rest tested. P. cystidiosus var. formosensis, P. ostreatus TENN 53662 and P. ferulaginis on the phylogenetic tree are more distinct from the rest i.e., Black pearl oyster and PC 15 and EM-1 grouping. Future studies are suggested to augment the reported findings in this thesis. Substrate (rice straw) composted for 10 days generally yielded higher growth rate especially samples supplemented with 30% w/w wheat bran. Same substrates composted for longer period (20 days) reduced mycelia growth rates. Despite differences in growth rates all the treatments achieved full colonization within 4 weeks. The varying supplement with sawdust (10 - 30% w/w) did not significantly (P≤0.05) influence growth rate of the mushroom. Sawdust-reduced mycelia composted for 21 days with 10% w/w wheat bran amendment was best to support optimum growth. Corn cob alone supported growth (35 mm/wk) commensurate with what obtained in the 1:2 w/w mixture with sawdust. The only difference was that the spawn run period was 5 days shorter with the unamended corn cob substrate. Ordinary paper supported growth but only a few pinheads (12) were formed and led to seven (7) fully formed carpophores with a Biological Efficiency of 58.3%. There were further flushes thereafter. Further studies should investigate other locally available agricultural waste materials beyond corn cob and sawdust and explore optimal substrate mixtures and ratios for maximum yield.