title: Enhancement and modeling of microparticle-added Rhizopus oryzae lactic acid production.
abstract: Lactic acid has a wide industrial application area and can be produced by fungal strains. However, excessive bulk growth form of fungi during the fermentations is a major problem, which limits the fermentation performance. Microparticles are excellent tools to prevent bulk fungal growth and provide homogenized fermentation broth to increase uniformity and the prediction performance of the models. Therefore, in this study, addition of aluminum oxide and talcum microparticles into fermentations was evaluated to enhance the production of lactic acid by Rhizopus oryzae. The results showed that the bulk fungal growth was prevented and the lactic acid concentration increased from 6.02 to 13.88 and 24.01 g/L, when 15 g/L of aluminum oxide or 10 g/L of talcum was used, respectively, in the shake-flask fermentations. Additionally, substrate concentration, pH, and agitation were optimized in the bioreactors using response surface methodology, and optimum values were determined as 126 g/L of glucose, 6.22 pH, and 387 rpm, respectively. Under these conditions, lactic acid production further increased to 75.1 ± 1.5 g/L with 10 g/L of talcum addition. Also, lactic acid production and glucose consumption in the batch fermentation were successfully modeled with modified Gompertz model and modified logistic model. RMSE and MAE values for lactic acid production were calculated as 2.279 and 1.498 for the modified Gompertz model; 3.6 and 4.056 for the modified logistic model. Additionally, modified logistic model predicted glucose consumption with -2.088 MAE and 2.868 RMSE, whereas these values were calculated as 2.035 and 3.946 for the modified Gompertz model.
authors.affiliation: Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, PA, 16802, USA. bugra44coban@gmail.com.
authors.forename: Hasan Bugra
authors.initials: HB
authors.lastname: Coban
authors.affiliation: Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.|The Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Demirci
mesh_terms: D000537:Aluminum Oxide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000096:biosynthesis*; D008954:Models, Biological; D012233:Rhizopus / Q000254:growth & development*; D013627:Talc / Q000494:pharmacology*
chemical_list: D013627:Talc; D019344:Lactic Acid; D000537:Aluminum Oxide
keywords: Lactic acid fermentation; Microparticle; Modeling; Optimization; Rhizopus oryzae