Effect of processing on the recovery of recombinant beta-glucuronidase (rGUS) from transgenic canola

This study addresses the processing of transgenic canola seed for productio n of recombinant proteins by using beta -glucuronidase (rGUS) as a model pr otein. The major processing steps that were investigated included dry and w et grinding of the seed, solvent extraction of canola oil, and protein extr action. rGUS in canola seed was stable for at least 2 weeks of incubation a t 38 degreesC and for more than 5 months at 10 degreesC. At 70 degreesC, th e residual activity changed inversely to the initial moisture content of th e seed. The comparison of wet and dry processing revealed no significant di fferences in protein recovery. rGUS was stable during the defatting of tran sgenic canola flakes with hexane at 66 degreesC, whereas 2-propanol extract ion at the same temperature reduced the extractable enzyme activity by almo st 50%. The particle size of the ground seed was important for the extracti on efficiency. A faster extraction and greater protein yield was achieved b y extracting particles with an average diameter equal to or smaller than 25 5 mum. More than 80% rGUS was extracted in one stage with sodium phosphate buffer of pH 7.5.