This research focused on the effect of temperature (25-75 degrees C), extraction time (40-120 min) and solvent/solid ratio (15-45 mL/g) and the enzyme assisted extraction on protein extraction efficiency from by-product of sugar beet. 3 different methods were applied in protein isolation and the highest protein yield (34.55%) was obtained by the isoelectric-ammonium sulfate precipitation method. At the optimized condition of temperature 54.25 degrees C, 81.35 min, and solvent/solid ratio of 27.65 mL/g, the protein yield was found 55.15%. The protein yield has reached 79.01% with an increase of 43.27% with the aid of the enzyme assisted extraction. The physicochemical properties were determined for revealing its potential use in food industry. It is promising that the isolated protein concentrates (SPC-IAP) show high protein content (69.08% d.b) as well as high solubility (98.71% at pH 7.5). SPC-IAP's high brightness (L* = 79.55), low redness (a* = 0.33) and low yellowness (b* = 13.27) values are encouraging for food industry.