Team:iBowu-China/Model
Modeling
Modeling for a better understanding of what factor we have to measure and what conversion yield we should aim at.
Due to insufficient experimental data, our modeling this year estimated the cost of using the enzymatic method to produce glycyrrhetinic acid, so as to deduce how much our yield needs to be lower than that of traditional chemical production methods. In the modeling, we use HP to access the data obtained. All price numbers mentioned herein are in units of RMB. The modeling work has been inspired by the methods used in reference [6].
In the cost estimation, the material cost we need to consider includes the market price of the reactant glycyrrhizic acid, the price of consumables required by the reaction system, the wages of workers required in industrial production, and the cost for building a factory, something we learned in interviews.
The market price of glycyrrhizic acid can be obtained by searching the Internet. In our industrial production, we do not consider high-purity glycyrrhizic acid. According to the search, the market price of 75% pure glycyrrhizic acid is 700,000/ton to 1 million/ton. For the convenience of estimation, we assume that the price is 850,000/ton and the unit is RMB. The current price of glycyrrhetinic acid on the market is about 4 million/ton.
The reaction system we chose is the Escherichia coli system, and the cost of the main consumables required is the cost of the LB medium. The dry powder of LB medium is about 300/kg, or 300,000/ton.
Here we need to know the best ratio of glycyrrhizic acid solution and enzyme solution when used in actual production before we can further estimate. We assume this ratio is Rl, the volume of required enzyme solution divided by the volume of GL solution.
The estimation of labor costs needs to take into account the number of people needed and the time required to complete the production of glycyrrhetinic acid. In addition to the experience, we have obtained in the HP interview, a common medium-scale factory takes about one year to produce 1 ton of chemical products and requires 3 workers. In Beijing, the annual wage cost of ordinary skilled workers is 72,000 per year, so the wage cost of workers is 216,000.
During the interview, we were not able to obtain data and experience related to the cost of building a plant. According to online searches, the investment required to build a medium-sized factory in Beijing is 5 million RMB. We assume that the investment cost is expected to be recovered in 10 years, then the cost per year is 500,000 RMB.
Our next estimate is to control the total production of 1 ton of glycyrrhetinic acid, and the estimated production time is 1 year. Under this condition, assuming that our enzyme converts glycyrrhizic acid into glycyrrhetinic acid under certain optimal conditions at an efficiency Rw. Then we have the following relations.
Figure 1. Equations of relation between the ratio of enzyme solution to reactant solution, and the conversion rate from (Glycyrrhizic acid) GL to (Glycyrrhetinic acid) GA.
Figure 2. A plot between Rw and Rl shows the possible area where enzymatic production of Glycyrrhetinic Acid would have lower cost.
It can be easily seen on the plot that only Rw and Rl values in the green shaded region, could it be possible to have a lower production cost, and thus make a profit for a company. Rl means the volume of enzyme solution when one converts one volume of glycyrrhizic acid, and this number is usually greater than one.
Rw, which is the conversion rate from glycyrrhizic acid to glycyrrhetinic acid, can not exceed unity. Therefore it exerted an extra constrain that the volume of enzyme solution used for conversion should be too large compared to the reactant. The conclusion agrees with our instinct.
One very important lesson we learned from this estimate is that in the lab we should test what is the optimal value of Rl is. Therefore our modeling provided a guideline for experimental works.
References
[1]. Jones, J., Vernacchio, V., Lachance, D. et al. ePathOptimize: A Combinatorial Approach for Transcriptional Balancing of Metabolic Pathways. Sci Rep 5, 11301 (2015). https://doi.org/10.1038/srep11301
[2]. Adams, A. M., Kaplan, N. A., Wei, Z. et al. In vivo production of psilocybin in E. coli. Metabolic Engineering, vol 56 p111-119, (2019). https://doi.org/10.1016/j.ymben.2019.09.009.
[3]. Afkhami-Poostchi A., Mshreghi, M., Iranshahi M., et al. Use of a genetically engineered E. coli overexpressing β-glucuronidase accompanied by glycyrrhizic acid, a natural and anti-inflammatory agent, for directed treatment of colon carcinoma in a mouse model. International Journal of Pharmaceutics, Vol 579, 119159 (2020). https://doi.org/10.1016/j.ijpharm.2020.119159.
[4]. Wang, X., Feng, X., Lv, B., et al. Enhanced yeast surface display of β-glucuronidase using dual anchor motifs for high-temperature glycyrrhizin hydrolysis. AIChE Journal. Vol 65, e16629 (2019).
[5]. Wang, Z., Pei, J., Li, H., and Shao, W.
Expression, Characterization and Application of Thermostable β-glucuronidase from Thermotoga maritima. Chin J Biotech Vol 24(8), 1407-1412 (2008).
[6]. Wang, Guojing. Enzymatic Production of Glycyrrhetinic Acid and the Separation Process Design. Master Thesis, Beijing Institute of Technology. (2016)
[7]. Brittona, J., Majumdar, S., and Weiss, G. A.
Continuous Flow Biocatalysis.
Chem Soc Rev. Vol 47(15): 5891–5918. (2018) doi:10.1039/c7cs00906b