The effect of chemical pretreatment combined with mechanical disruption on the extent of disruption and release of intracellular protein from E. coli

The combination of non-mechanical (chemical) and mechanical methods such as high pressure homogenisation (HPH) can increase the release of intracellular components and decrease the exposure to mechanical disruption required for the breakage to attain maximum intracellular release. Through these, the energy requirement of microbial cell disruption can be decreased along with the reduction in the micronisation of cell debris. Pretreatments to permeabilise or weaken the cell envelope were selected and the optimum conditions determined through a screening process. The permeabilisation of Escherichia coli with EDTA was successful in achieving maximum intracellular protein release at a lower pressure of 13.8 MPa on high pressure homogenisation, compared with 34.5 MPa in the absence of EDTA. Significant reduction in energy input required was observed with the use of this combination method. Pretreatment with guanidium hydrochloride (G-HCl) and Triton X-100 also resulted in increased intracellular release and decreased energy usage. Chemical pretreatment can be useful in enhancing mechanical disruption, however, careful selection of pretreatment conditions is required to avoid protein deactivation and chemical interference in the protein assay.