. The aim of this study was to investigate the potential of producing liquid spawn of an edible mushroom,Pleurotus pulmonarius (grey oyster) by submerged fermentation in a 2-L stirred-tank bioreactor under controlled conditions and to evaluate its ability to colonise rubber wood sawdust substrate for sporophore production. The liquid spawn cultivation medium contain 20 g L−1 of brown sugar, 4 g L−1 of rice bran, 4 g L−1 of malt extract, and 4 g L−1 of yeast extract (BRMY) with initial pH of 5.5 and incubated at 28 °C with agitation speed of 250 rpm and oxygen partial pressure of 30–40%. Maximum P. pulmonarius dry biomass production of 11.72 ± 5.26 g L−1 was achieved after 3 days of fermentation. The liquid spawn has the ability to colonise sterile rubber wood sawdust as fruiting substrates in a shortened time and produced higher yield of sporophores compared to the traditionally used grain spawn.