Optimization the Alginate Production Conditions in Sweet Whey Medium by Azotobacter Chrococcum

Abstract

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.

Production of biodegradable microbial polymers from whey

“…Under optimised conditions (pH, salt concentrations, T 0 ) alginate concentrations above 5 g/L (0.05 g/L/h) were achieved, albeit with longer cultivation times and at a higher (35 °C) temperature. The aforementioned results indicate that both A. chrococcum producer strains have sufficient β-galactosidase activity, as nonhydrolysed CW is well-utilised for alginate synthesis (Hendawy et al 2019;Khanafari et al 2007). In contrast, another producer, Azotobacter vinelandii ATCC9046, was able to use only hydrolysed and deproteinised CW as the carbon source (reducing sugars 20 g/L), and only part of the galactose was utilised from hydrolysed lactose (Trujillo-Roldán et al 2015).…”

“…Whilst most alginates are still derived from seaweed and algae, there is an increasing focus on their microbiological production, including the use of renewable resources (Urtuvia et al 2017). However, currently only a few studies have evaluated the use of CW and its derivatives for microbiological production of alginates (Khanafari et al 2007Trujillo-Roldán et al 2015Hendawy et al 2019). Thus, the producer strain Azotobacter chrococcum NCBI MH249629 using the culture medium with deproteinised sweet whey (lactose 45 g/L) in shake flasks and under optimised conditions (concentration of lactose and nitrogen sources, pH, T 0 , agitation speed, cultivation time) achieved the alginate concentration of 5.65 g/L (0.08 g/L/h) (Hendawy et al 2019), which is Table 2 Comparatively efficient microbial production of polyhydroxyalkanoates (PHAs) from whey and whey-derived products a)…”