Vol.:(0123456789) 1 3 Bioprocess and Biosystems Engineering https://doi.org/10.1007/s00449-018-1952-x RESEARCH PAPER Development of a cost-efective production process for Halomonas levan Burak Adnan Erkorkmaz 1  · Onur Kırtel 1  · Özlem Ateş Duru 2  · Ebru Toksoy Öner 1 Received: 14 March 2018 / Accepted: 6 May 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Levan polysaccharide is an industrially important natural polymer with unique properties and diverse high-value applica- tions. However, current bottlenecks associated with its large-scale production need to be overcome by innovative approaches leading to economically viable processes. Besides many mesophilic levan producers, halophilic Halomonas smyrnensis cultures hold distinctive industrial potential and, for the frst time with this study, the advantage of halophilicity is used and conditions for non-sterile levan production were optimized. Levan productivity of Halomonas cultures in medium contain- ing industrial sucrose from sugar beet and food industry by-product syrup, a total of ten sea, lake and rock salt samples from four natural salterns, as well as three diferent industrial-grade boron compounds were compared and the most suitable low-cost substitutes for sucrose, salt and boron were specifed. Then, the efects of pH control, non-sterile conditions and diferent bioreactor modes (batch and fed-batch) were investigated. The development of a cost-efective production process was achieved with the highest yield (18.06 g/L) reported so far on this microbial system, as well as the highest theoretical bioconversion efciency ever reported for levan-producing suspension cultures. Structural integrity and biocompatibility of the fnal product were also verifed in vitro. Keywords Exopolysaccharide · Levan · Halomonas smyrnensis · Microbial bioprocess · Cost-efective production Introduction Levan is a fructose-based homopolysaccharide, a fructan that is mainly composed of β-D-fructofuranose residues linked by β-(2–6) glycosidic bonds. It serves both struc- tural and functional roles and stands out from other natural polymers by its unique combination of properties such as strong adhesivity, self-assembly into spherical colloids, very low intrinsic viscosity and high biocompatibility, which in turn make this unusual polysaccharide a valuable polymer for various applications in cosmetic, pharmaceutical, food and other industries [1]. Several studies also indicated the potential benefcial efect of levan as prebiotic on human and other animal’s intestinal microbial community [2–4]. For instance, Hamdy et al. [5] reported that levan could be used as symbiotics resulting in optimum liver protection against pathogen complications due to its benefcial interactions with probiotics. While levan is produced by a limited number of plant species at low degree of polymerization (DP 10–100), longer levan chains (> DP 10 3 –10 4 ) that ofer broader range of applications are produced by miscellaneous microorganisms both extracellularly and at high titers from sucrose by the transfructosylation activity of levansucrase enzyme [6, 7]. Besides mesophilic levan producers from a wide range of genera that include Acetobacter, Bacillus, Erwinia, Gluconobacter, Microbacterium, Pseudomonas, Zymomonas, it can be also produced by many acetic acid and lactic acid bacteria. Among these diferent kinds of organisms, Halomonas cultures hold distinctive industrial potential due to their added advantages such as high yield and non-sterile production capacity under high salinity [8, 9]. The frst extremophilic producer and novel spe- cies, Halomonas smyrnensis AAD6 T , has been shown to produce levan at high titers [10]. Subsequent studies on levan produced by these cultures (hereafter abbreviated HL) revealed that it displays anti-oxidant, anti-cancer [11] * Ebru Toksoy Öner ebru.toksoy@marmara.edu.tr 1 IBSB-Industrial Biotechnology and Systems Biology Research Group, Department of Bioengineering, Marmara University, Goztepe Campus, 34722 Istanbul, Turkey 2 Nişantaşı University, 34485 Istanbul, Turkey