In this study

genome shuffling of eight original strains obtained by various methods of chemical and physical mutations was used to achieve rapid improvement of spinosad production. The conditions of preparation

regeneration

parents inactivation and fusion of protoplast of the original strain were investigated. The strain grown for 65 h was treated by 4 mg·ml-1 lysozyme at 39℃ for 20 min

and preparation rate and regeneration rate were 92.30% and 7.66%

respectively. The protoplasts were inactivated by heating at 60℃ for more than 90 min and UV treatment more than 200 s

respectively. The inactivated protoplasts were fused and regenerated in polyethylene glycol (PEG 6000

50%) for 15 min

and fusion rate was about 1.18%. After three rounds of genome shuffling

a high yielding strain

designated as S.spinosa 3-652

was isolated. The increased yield was about 36.07% higher than that of the original strain. Subculture experiments indicated that the high producers were stable.