Study On Extractive Fermentation For Production Of Welan Gum By Alcaligenes Sp. ATCC31555 In Cloud Point System

Welan gum is a microbial polysaccharidesecrete by Alcaligenessp.ATCC31555 The primary structure units of welan gum consists of L-glucuronic acid, L-glucose and L-rhamnose. Because of its unique rheological properties and molecular structure, welan gum has much potential on the buildings, food, oil, and other fields. Welan gum was developed by American Kelco corporation with series ofgellan gum and xanthan gum in the 1980 s, which has a big market reuqirement.Currently, welan gum fermentation in Alcaligenes is suffering from low yield and high cost, which limits the large-scale production and applications. In this paper, Alcaligenes sp. ATCC31555 as the starting strain, production inhibition is removed by non-ionic surfactants through extracting the welan gum from inner membrane to outer membrane,which eliminated the product inhibition and prevented the product from further degradation. Meanwhile, the viscosity of fermentation broth greatly decreased by the emulsification in non-ionic surfactant, the concentration of welan gum continuously increased with stable viscosity. Six non-ionic surfactants including Triton X-114, Triton X-100, Triton X-45, Tween 80, Brij 30 and Tergitol TMN-3 were chosen for welan gum production by Alcaligenes sp. ATCC31555. The optimal fermentation conditions were as follows: fermentation temperature 30 ℃, 300 rpm, addition of non-ionic after fermentation for 36 h and dosage of 3ml / 100 ml. After fermentation for 72 h, Triton X-114 was found to be best non-ionic surfactant in cloud point system. Compared to the control group,welan gum production increased by 100%.Secondly, in the case of Triton X-114 addition in culture system, the optimized conditions were as follows:7ml Triton X-114 into 100ml broth after fermentation for 30-36 h.The highest welan gum concentration with 52.0±2.5 g/L was obtained after fermentation for 120 h, the yield was up to 0.867±0.042g?g-1which is currently the highest level.Thirdly,we also recovered the Triton X-114 by distilling.The results showed that the recovery of Triton X-114 can be reused twiceand also keep the higher welan gum production.Finally, the rheological properties of welan gum samples from Triton X-114 cloud point extraction fermentation were studied,, the effects of temperature, salt, PH. The results showed that the quality of extractive fermentation production of welan gum did not change.