Dextran Utilization During Its Synthesis by Weissella cibaria RBA12 Can Be Overcome by Fed-Batch Fermentation in a Biore
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Dextran Utilization During Its Synthesis by Weissella cibaria RBA12 Can Be Overcome by Fed-Batch Fermentation in a Bioreactor Rwivoo Baruah 1 & Barsha Deka 1 & Niharika Kashyap 2 & Arun Goyal 1,2
Received: 24 February 2017 / Accepted: 19 May 2017 # Springer Science+Business Media New York 2017
Abstract Weissella cibaria RBA12 produced a maximum of 9 mg/ml dextran (with 90% efficiency) using shake flask culture under the optimized concentration of medium components viz. 2% (w/v) of each sucrose, yeast extract, and K2HPO4 after incubation at optimized conditions of 20 °C and 180 rpm for 24 h. The optimized medium and conditions were used for scale-up of dextran production from Weissella cibaria RBA12 in 2.5-l working volume under batch fermentation in a bioreactor that yielded a maximum of 9.3 mg/ml dextran (with 93% efficiency) at 14 h. After 14 h, dextran produced was utilized by the bacterium till 18 h in its stationary phase under sucrose depleted conditions. Dextran utilization was further studied by fed-batch fermentation using sucrose feed. Dextran on production under fed-batch fermentation in bioreactor gave 35.8 mg/ml after 32 h. In fed-batch mode, there was no decrease in dextran concentration as observed in the batch mode. This showed that the utilization of dextran by Weissella cibaria RBA12 is initiated when there is sucrose depletion and therefore the presence of sucrose can possibly overcome the dextran hydrolysis. This is the first report of utilization of dextran, postsucrose depletion by Weissella sp. studied in bioreactor. Keywords Weissella cibaria . Dextran . Sucrose . Bioreactor
* Arun Goyal [email protected]
1
Carbohydrate Enzyme Biotechnology Laboratory, Department of Bioscience and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039 Assam, India
2
Center for the Environment, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
Appl Biochem Biotechnol
Introduction Lactic acid bacteria belonging to genera Lactobacillus, Leuconostoc, Streptococcus, Pediococcus, and Weissella have been reported to produce an extracellular homopolysaccharide named dextran using sucrose as a substrate [1]. Dextran is composed of glucose monomers that are linked by α-(1 → 6) glycosidic bonds in the main chain with different degrees of α-(1 → 2), α-(1 → 3), and α-(1 → 4) glycosidic bonds as branched linkages [2]. Among the several genera mentioned above, genus Weissella has a distinctive phenotypic feature to produce dextran in the presence of sucrose [3, 4]. Most notably, Weissella confusa and Weissella cibaria are among the most prolific dextran producers [5]. Dextrans produced by genus Weissella have been reported to have similar structures, consisting of mostly α-(1 → 6) glycosidic bonds and a few α-(1 → 3) glycosidic bonds as branched linkages (2.4–7.0%) [6–8]. Dextran from genus Weissella is also attributed with high molecular weight ranging from 800 kDa [9] to 36 MDa [10]. The presence of low degree of branching and high molecular weight of dextran from Wei
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