Research Article Process design and economic studies of two‑step fermentation for production of ascorbic acid Shi Min Lim1 · Michelle Siao Li Lau1 · Edward Ing Jiun Tiong1 · Mun Min Goon1 · Roger Jhee Cheng Lau1 · Wan Sieng Yeo1 · Sie Yon Lau1 · Nabisab Mujawar Mubarak1 Received: 7 November 2019 / Accepted: 26 March 2020 / Published online: 5 April 2020 © Springer Nature Switzerland AG 2020 Abstract The current study presents the conceptual design of a chemical plant for an annual production of 500 tonne ascorbic acid or Vitamin C with a high purity of 95% via fermentation of D-sorbitol. In this study, two-step fermentation with a single culture process is operated with a proper ISO 14000 Environmental Management procedure. A process fow diagram of the processing plant and the plant-wide simulation fowsheet that was generated by SuperPro Designer Simulation software, as well as the material and energy balances are also depicted. Meanwhile, the process is optimized through the recycling of sorbose and heat integration. By recycling sorbose, the production of ascorbic acid has increased by 24% while the total energy consumption had reduced by 20% after heat integration. Furthermore, economic and sen- sitivity analysis was performed to calculate the proftability of the plant and predict the efect of market conditions on the investments. After the economic analysis, total capital investment and total production cost for the best scenario were found to be roughly USD 52 million and USD 43 million, respectively with a return on investment of 78.73% and a payback period of 1.17 years since the selling price of Vitamin C is high. Keywords Ascorbic acid · SuperPro Designer · Fermentation · Biomass · Esterifcation · Economic analysis Abbreviations NaOH Sodium hydroxide Cc Concentration of biomass NPV Net present value CO2 Carbon dioxide OL Operating labour Cp Specifc heat capacity OS Operating supervision CSTR Continuous stirred tank reactor PE Purchased equipment DC Direct cost PED Purchased equipment delivered FC Fixed charges P&ID Piping and instrumentation diagram FCI Fixed capital investment POC Plant overhead cost GCE Glassy carbon electrode Pt Platinum GE General expenses ROI Return on investment H2O Water SF Scale factor IC Indirect cost T Temperature MC Maintenance and repairs cost Tc Critical temperature MnOx-MoOx Manganese and molybdenum mixed TCI Total capital investment oxides TMC Total manufacturing cost NaHCO3 Sodium bicarbonate TPC Total production cost * Wan Sieng Yeo, [email protected] | 1Department of Chemical Engineering, Curtin University Malaysia, CDT 250, 8009 Miri, Sarawak, Malaysia. SN Applied Sciences (2020) 2:816 | https://doi.org/10.1007/s42452-020-2604-8 Vol.:(0123456789) Research Article SN Applied Sciences (2020) 2:816 | https://doi.org/10.1007/s42452-020-2604-8 V Working volume of fermenter as the largest producer, followed by the United States and VPC Variable production cost Western Europe. The price of 70% sorbitol solution of phar- maceutical grade is approximately USD 500 per tonne. The market size of sorbitol was around 1.85 million tonne in 1 Introduction the year 2015. It is expected to reach 2.4 million tonne by the year 2023, with a compound annual growth rate Ascorbic acid (Vitamin C) is the most abundant natural of 3.5% from the years 2016 to 2023. The major sorbitol hydro-soluble antioxidant used as a dietary supplement producer companies in the market are Archer Daniels Mid- for the human [1], and it exists in various fruits and veg- land, Cargill, Ingredion, Roquette and Tereos. etables such as lemons, oranges, and broccoli. Also, it is an essential cofactor for various metalloenzymes in the 2.1 Raw materials and prices human body [2]. Besides, ascorbic acid is required by the agriculture, food, beverage and pharmaceutical industries The feedstocks to produce ascorbic acid include corn, due to its antioxidant properties. The largest consumer wheat, molasses and D-sorbitol. Meanwhile, the current of ascorbic acid is the pharmaceutical industry, which is price for corn is USD 146 per tonne, wheat is USD 232 one-third of its total production. The market demand of per tonne, molasses is USD 261 per tonne, and sorbitol ascorbic acid has grown steadily in the Asia Pacifc region, is approximately USD 500 per tonne. Pre-treatment is including China, Japan, and India, followed by Europe and required to extract glucose from corn, molasses and wheat North America due to the increasing awareness of the before the conversion of glucose into D-sorbitol. public towards a healthy and quality lifestyle. Based on the global Vitamin C report, the global revenue of ascorbic 2.2 Process technology selection acid market has grown drastically from USD 1070 million in the year 2014 to USD 1280 million in the year 2017, with an The three available process technologies used to pro- average annual growth rate of 6.16%. Moreover, it contin- duce ascorbic acid are the Reichstein process, the two- ues to grow and reach USD 1770 million by the year 2022. step fermentation with a single culture, and the two-step Ascorbic acid can be synthesized via the Reichstein fermentation with a mixed culture. These process tech- process or two-step fermentation process with a single or nologies have a similar overall yield of production, which mixed culture [3]. In this plant design, the two-step fer- is 60%. However, the two-step fermentation has higher mentation process with a single culture is selected since efciency and product quality than the Reichstein process it is environmental-friendly, as well as it has lesser toxic- [6]. In terms of process technologies economy, the atom ity and lower cost as compared to the Reichstein process economy values for the Reichstein process and two-step [4]. By-products produced from chemical reactions of the fermentation are 0.6424 and 0.5383, respectively. Atom selected process are sodium hydroxide (NaOH) and carbon economy is the conversion efciency of a chemical pro- dioxide (CO2). Meanwhile, the concentrated sulphuric acid cess in terms of all atoms involved and the desired prod- is the hazardous chemical involved in this process. Besides, ucts produced. Lower capital and operating costs of the the water (H 2O) released from the process are sent to a two-step fermentation process outweigh its lower atom wastewater treatment plant before it is discharged, which economy; therefore, the overall revenue of the two-step is in accordance with the Environmental Quality Act 1974 fermentation is higher than the Reichstein process. The [5]. The objective of this study is to design an ascorbic acid calculation of atom economy for the two-step fermenta- production plant with a capacity of 500 tonne per year, tion process is shown in Table a1 in the Appendix. 60% target product recovery, and high purity of 95%. The chemical equation for the Reichstein process is shown as Eq. (1): C H O 1 2O NaHCO → C H O 2 Materials and Method 6 14 6 + ∕ 2 + 3 6 8 6 NaOH CO 2H H O + + 2 + 2 + 2 (1) Ascorbic acid is produced from D-sorbitol, a sugar alco- Sorbitol + Oxygen + Sodium bicarbo- hol that can be obtained from various feedstock such as nate → Sorbose + Sodium hydroxide + Carbon corn, cassava and wheat. Sorbitol is commonly used in the dioxide + Hydrogen + Water. industrial manufacturing of toothpaste, toiletries, food and The chemical equation for the two-step fermentation ascorbic acid. The global sorbitol production capacity is process (for a single culture and a mixed culture) is shown approximately 500 kilo tonne in the year 2013 from China as Eq. (2): Vol:.(1234567890) SN Applied Sciences (2020) 2:816 | https://doi.org/10.1007/s42452-020-2604-8 Research Article C6H14O6 + 3∕2O2 + Na2CO3 + NaHCO3 the two-step fermentation is simpler with lesser steps, lower → C H O 3NaOH 2CO 2H O capital and operating cost, as well as it works at a lower tem- 6 8 6 + + 2 + 2 (2) perature and pressure conditions than the Reichstein process. Reichstein process has a higher conversion efciency of Hence, the two-step fermentation with a single culture or a reactant to products as compared to the two-step fermen- mixed culture is more preferred than the Reichstein process. tation process. However, the capital and operating costs of Next, the single culture and the mixed culture of the two-step fermentation are much lower than the Reichstein two-step fermentation process are studied and com- process, and this outweighs its lower atom economy and pared. In the second fermenter, the single culture only conversion efciency [7]. Moreover, in the Reichstein pro- uses one bacterium, whereas the mixed culture uses two cess, sorbitol in the conventional batch fermenter inhibits diferent bacteria. However, the mixed culture is hard to the growth of bacteria and high initial concentration of be detected and controlled the contamination of the fer- sorbitol decrease the rate of oxidation [8]. The overall pro- mentation. Moreover, it is difcult to obtain an optimum duction cost of the two-step fermentation process is two- balance among the microorganisms involved [10], and the third of the Reichstein process. In other words, the total cultivation of two diferent bacteria requires more time revenue of the two-step fermentation process is higher. and space. Therefore, the two-step fermentation with a Besides, as shown in the process fow diagram (Fig. 6) single culture is chosen since it has a lower production in Appendix, the two-step fermentation process involves cost with higher efciency, and it is easier to control and lesser steps than the Reichstein process; thus, it reduces monitor the fermentation process than the mixed culture. energy and water consumptions. Also, the two-step fermen- tation process operates at lower temperature and pressure 2.3 Process description conditions, which is cheaper and safer than the Reichstein process.