Biochemical Engineering Journal 48 (2010) 166–172 Contents lists available at ScienceDirect Biochemical Engineering Journal journal homepage: www.elsevier.com/locate/bej Biodegradation kinetics and modeling of whey lactose by bacterial hemoglobin VHb-expressing Escherichia coli strain Muayad M. Abboud a , Isam H. Aljundi b,∗ , Khaled M. Khleifat c , Saif Dmour c a Pharmacology Department, Mutah University, Al-Karak 61710, Jordan b Chemical Engineering Department, Mutah University, Al-Karak 61710, Jordan c Biology Department, Mutah University, Al-Karak 61710, Jordan article info Article history: Received 21 July 2009 Received in revised form 17 September 2009 Accepted 27 September 2009 Keywords: Whey lactose biodegradation E. coli strain VHb Fermentation Kinetic models Haldane equation abstract The batch fermentation of cheese whey lactose was achieved using Escherichia coli:pUC8:16 recombi- nant strain that was transformed with Vitreoscilla hemoglobin gene(vgb). In this process, 70% of the initial whey lactose was biodegraded during 24 h of incubation time. Biodegradation was accompanied with a turnover of glucose intermediate and a production of lactic acid. Total lactic acid produced by this recombinant strain was 57.8 mmol/L compared with a reference lactic acid producing strain, Lactobacillus acidophilus, that yielded only 55.3 mmol/L of lactic acid from the same initial whey lactose concentra- tion. The engineering of vgb gene transformation in E. coli strain has led to increase in bacterial biomass and boosted lactic acid production, relative to other strains that lack the vgb gene like E. coli:pUC9 or E. coli wild type or Enterobacter aerogenes. Contrary to Monod’s, Haldane’s model gave a good fit to the growth kinetics data. Kinetic constants of the Haldane equation were  m = 0.5573 h -1 , K s = 4.8812 g/L, K I = 53.897 g/L. Biomass growth was well described by the logistic equation while Luedeking–Piret equa- tion defined the product formation kinetics. Substrate consumption was explained by production rate and maintenance requirements. In simulation studies including the Haldane model, an evident agree- ment was observed between measured and calculated biomass, product, and substrate concentrations. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Whey is a watery by-product of the cheese manufacturing pro- cess which is composed mainly of 5–6% lactose and 0.8–1% protein [1,2]. It is produced world wide in large quantity reaching over 10 8 tons per year [3]. Cheese whey is considered environmentally high strength wastewater pollutant due to its high biological oxy- gen demand (BOD) and chemical oxygen demand (COD) contents which approaches values of 50 and 80 g/L, respectively [4]. The disaccharide lactose is the major carbohydrate of milk and dairy products. It can be considered as a renewable and thus biotechnologically important carbon source which accumu- lates primarily as a by-product from cheese manufacture or whey processing industries [5]. Only 56% of the whole whey solids are currently processed into animal or human food products [6]. Several problems are encountered in whey disposal, including uneconomical transport due to its high water content and the difficulty of prolonged storage because of whey susceptibility to spoilage by bacteria and fungi. In addition, drying the whey requires ∗ Corresponding author. Tel.: +962 3 2372380; fax: +962 3 2375540. E-mail address: aljundi@mutah.edu.jo (I.H. Aljundi). a large capital investment and energy consumption which are not economically profitable [7]. Therefore, the currently adopted biotechnology of whey disposal is based on recycling of the main nutrient components: lactose and proteins. There has been increased interest in lactic acid production from whey lactose, because of its utilization as raw material for the production of polylactic acid polymer that has special industrial applications in manufacturing medical and biodegradable plas- tics [8]. Lactic acid can be produced either by chemical synthesis or fermentative processes [9,10] but the fermentative means has advantages over chemical synthesis, due to a better efficiency and desirable optically pure lactic acid being generated [11]. Usually the complete fermentation of whey lactose requires the supplementa- tion of whey with an additional nitrogen source such yeast extract or whey protein hydrolyzate in order to insure rapid production of lactic acid [12–14]. Various bacterial and fungi microorganisms are capable of pro- ducing Lactic acid from whey lactose disposal [15–18], however few efforts have been made to improve the production of lactic acid through metabolic engineering techniques. One such attempt was conducted involving the expression of l-lactate dehydrogenase and d-lactate dehydrogenase genes in L. helveticus for the produc- tion of pure d(-)- and l(+)-lactic acids [19]. In another attempt, a 1369-703X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.bej.2009.09.006