Age of selected spores
The age of selected spores not only has a great influence on the growth state, but also affects the expression level of cells. Porcel et al.(Porcel, López et al. 2006) found a higher titer for lovastatin production by using older spores. The titer of lovastatin increased by 52% to 186.5±20.1 mg/L when the age of inoculated spores increased from 9 days to 16 days.