title: High cell density cultivation of probiotics and lactic acid production.
abstract: The commercial interest in functional foods that contain live microorganisms, also named probiotics, is paralleled by the increasing scientific attention to their functionality in the digestive tract. This is especially true of yogurts that contain strains of lactic-acid bacteria of intestinal origin, among these, Lactobacillus delbrueckii ssp. bulgaricus is extensively used in the dairy industry and it has been demonstrated to be a probiotic strain. In this work we describe high cell density cultivations of this microorganism also focusing on the stereospecific production of lactic acid. Key parameters such as medium composition (bactocasitone concentration) and diverse aeration conditions were explored. The results showed that the final concentration of biomass in anaerobic fermentation was lower than the one obtained in microaerophilic conditions, while it gave a very high productivity of lactic acid which was present as a racemic mixture in the permeate. Fermentation experiments carried out with air sparging, even at very low flow-rate, led to the production of the sole L(+) lactic acid giving sevenfold increase in biomass yield in respect to the batch cultivation. Finally, a mathematical model was developed to describe the microfiltration bioprocess applied in this research considering an inhibition kinetic and enucleating a suitable mathematical description for the decrease of the transmembrane flux.
authors.affiliation: Department of Experimental Medicine, Faculty of Medicine, Second University of Naples, Via Costantinopoli 16-80138, Naples, Italy. chiara.schiraldi@unina2.it
authors.forename: Chiara
authors.initials: C
authors.lastname: Schiraldi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Adduci
authors.forename: Vivien
authors.initials: V
authors.lastname: Valli
authors.forename: Carmelina
authors.initials: C
authors.lastname: Maresca
authors.forename: Mariateresa
authors.initials: M
authors.lastname: Giuliano
authors.forename: Monica
authors.initials: M
authors.lastname: Lamberti
authors.forename: Maria
authors.initials: M
authors.lastname: Cartenì
authors.forename: Mario
authors.initials: M
authors.lastname: De Rosa
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D003198:Computer Simulation; D019344:Lactic Acid / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D007778:Lactobacillus / Q000254:growth & development* / Q000378:metabolism*; D008567:Membranes, Artificial; D008954:Models, Biological; D019936:Probiotics / Q000378:metabolism; D013237:Stereoisomerism; D014462:Ultrafiltration / Q000295:instrumentation / Q000379:methods
chemical_list: D008567:Membranes, Artificial; D019344:Lactic Acid