Sweet whey was used as medium for microbial alginate production by Azotobacter chrococcum NCBI MH249629. To optimize alginate production and achieve high yield of alginate, sweet whey medium was prepared using different lactose concentrations (20, 25, 30, 35, 40, 45, 50 g/L), added organic and inorganic nitrogen sources (yeast extract, Malt extract, ammonium sulphate and ammonium nitrate), kept at different temperatures (25, 30, 32, 35 & 37ºC), different pH values (4, 5, 6, 7, 8, 9), different agitation speed (100, 120, 150, 170 & 200 rpm), different inoculum size (1,2,3,4,5,6,7,8,9,10%) and cultivated for different fermentation time (0, 12, 24, 36, 48, 60, 72, 84, 96, 108 & 120h). After fermentation time, produced microbial alginate was measured. The results showed that sweet whey could be used as a fermentation medium by Azotobacter chrococcum to produce microbial alginate. The highest yield of alginate (12.56%) as well as productivity of alginate (0.08 g/L/h) was obtained by fermentation of Azotobacter chrococcum in sweet whey medium optimized to 45 g/L lactose concentration as a carbon source and by providing the following conditions which yeast extract 1.5 g/L and ammonium nitrate 0.1 g/L as a nitrogen source and growth promoter, Na2HPO4 1 g/L as mineral salts, Initial pH at 7, size of standard inoculums was 9 % of fermentation medium and the incubation period was 72 hrs.
