title: Resistance of Lactobacillus casei in plastic-composite-support biofilm reactors during liquid membrane extraction and optimization of the lactic acid extraction system.
abstract: Lactic acid fermentations were performed with plastic-composite-support (PCS) disks in solvent-saturated media with Lactobacillus casei subsp. rhamnosus (ATCC 11443). The PCS disks contained 50% (w/w) polypropylene, 35% (w/w) ground soybean hulls, 5% (w/w) yeast extract, 5% (w/w) soybean flour, and 5% (w/w) bovine albumin. Bioassays were performed by growing L. casei in solvent-saturated media after soaking the PCS disks. Eighteen different solvent and carrier combinations were evaluated. Overall, L. casei biofilm fermentation demonstrated the same lactic acid production in solvent-saturated medium as suspended cells in medium without solvents (control). To evaluate PCS solvent-detoxifying properties, two bioassays were developed. When solvent-saturated medium in consecutive equal volumes (10 mL then 10 mL) was exposed to PCS, both media demonstrated lactic acid fermentation equal to the control. However, when solvent-saturated medium with two consecutive unequal volumes (10 mL then 90 mL) was exposed to PCS, some degree of toxicity was observed. Furthermore, iso-octane, tributylphosphate (TBP), and Span 80 were optimized for recovery as 91%, 5%, and 4% (v/v), respectively, with a 1:1 ratio of 1.2 M Na(2)CO(3) stripping solution. Also, recovery by emulsion liquid extraction in the hollow-fiber contactor was minimal due to low recovery at pH 5.0 and incompatibility of the solvent and hollow-fiber material. These results suggest that PCS biofilm reactors can benefit lactic acid fermentation by eliminating the toxic effect from solvent leakage into the fermentation medium from liquid-liquid extractive integrated fermentations.
authors.affiliation: Department of Agricultural and Biological Engineering, Pennsylvania State University, University Park, PA 16802, USA. demirci@psu.edu
authors.forename: Ali
authors.initials: A
authors.lastname: Demirci
authors.forename: Julie C
authors.initials: JC
authors.lastname: Cotton
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Pometto
authors.forename: Kristi R
authors.initials: KR
authors.lastname: Harkins
authors.forename: Paul N
authors.initials: PN
authors.lastname: Hinz
mesh_terms: D018441:Biofilms; D019149:Bioreactors; D003470:Culture Media; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology / Q000379:methods*; D019344:Lactic Acid / Q000378:metabolism*; D007780:Lacticaseibacillus casei / Q000254:growth & development / Q000378:metabolism*; D008567:Membranes, Artificial; D010969:Plastics; D012997:Solvents / Q000737:chemistry / Q000633:toxicity*
chemical_list: D003470:Culture Media; D008567:Membranes, Artificial; D010969:Plastics; D012997:Solvents; D019344:Lactic Acid