The objective of this study was to substitute cotton pretreatment chemicals with enzymes to create an environmentally friendly process for water and energy savings. In this study, enzyme selection and process optimisation was made in order to increase the glucose content of the desizing liquor of a starch-sized cotton fabric. Results indicated that commercial desizing enzyme formulations of a-amylase enzymes were not appropriate to produce a large quantity of glucose in the desizing bath; the glucose amounts obtained were about 200 mg/l. However the food market enzyme used, an amyloglucodidase/pullanase mixture (amyloglucosidase 186 Units/g, pullanase 395 Units/g), produced approximately 4000 mg/l glucose in the desizing bath after process optimisation. The desizing effect of the amyloglucodidase/pullanase enzyme mixture was compatible with those of commercial desizing enzymes. The results of peroxide generation from glucose and bleaching trials are reported in the second part of the study.