(617e) Enhancing Poly(3HB-co-4HB) Production: Incorporating Multiscale Model into MPC to Control Molecular Weight Distributions and Monomeric Ratios

While petroleum-derived plastic materials have brought significant convenience into the daily life of mankind, they are predominantly non-renewable and unsustainable. Despite their easy production, their disposal poses serious environmental risks, including air/water pollution, greenhouse gas emissions, and the release of toxic substances [1], highlighting the urgent need for eco-friendly polymer alternatives. To overcome this issue, the exploration of bio-based polymer production, particularly, polyhydroxyalkanoates (PHAs), has attracted research interests due to their biocompatibility, synthesis from natural resources, and marine degradability [2].

Among diverse PHAs, the 3-hydroxybutyrate (3HB) homopolymer is well recognized and utilized. Nevertheless, its brittleness and stiffness limit its usability, necessitating the development of more adaptable varieties [3]. In this sense, some PHA variants such as poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) have been developed [4]. It can offer more flexibility and its properties can be tuned by controlling their monomeric composition. However, there are many factors determining their physical properties. To address this, a multiscale kMC model was developed to elucidate the intricate polymerization dynamics of P(3HB-co-4HB) [5].

As biopolymer production involves cell metabolism and polymerization, the overall process was modeled with the two-layer structure, handling significant difference in their length/time scales. The first layer was modeled by a series of differential equations coupled with Monod equation. This is categorized as macroscopic reactions, including the carbon source consumption, monomer production, by-product generation, as functions of pH, feed rate, temperature [6]. Produced biomass (e.g., synthase) and monomers are introduced in the microscopic kMC layer as reacting particles. In each time step, the rates of initiation, elongation, termination, and depolymerization were evaluated. Subsequently, the particles interact and form specific molecular weight distribution (MWD) and monomeric composition. This multiscale model was not only validated against the pilot-scale lab experiments, but also shown the outstanding capabilities of capturing MWDs and their monomeric compositions.

Subsequently, the multiscale model is seamlessly incorporated into the model predictive control (MPC) framework. This novel approach achieves unprecedented control performance with delicate objectives – including precise regulation of MWD and monomeric ratios – surpassing the limitations of average-value controls. This result highlights the effective coupling of the multiscale model with MPC, taking advantage of the strengths of both strategies to offer a comprehensive control solution. In conclusion, this work will shed light on developing an advanced control strategy in complex, multiscale reaction systems. Also, it provides substantial enhancements in efficiency and sustainability in biopolymer production to reduce environmental impacts markedly.

Literature cited:

[1] Ewing T.A., Nouse N., van Lint M., van Haveren J., Hugenholtz J., & van Es D.S. (2022). Fermentation for the production of biobased chemicals in a circular economy: a perspective for the period 2022-2050. Green Chem., 24, 6373-6405.

[2] Naser A.Z., Deiab I., & Darras B.M. (2021). Poly(lactic acid) (PLA) and polydydroxyalkanoates (PHAs), green alternatives to petroleum-based plastics: a review. RSC Adv., 11, 17151-17196.

[3] Chotchindakun K., Pathom-Aree W., Dumri K., Ruangsuriya J., Pumas C., & Pekkoh J., (2021). Low crystallinity of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) bioproduction by hot spring cyanobacterium Cyanosarcina sp. AARL T020. Plants, 10, 503.

[4] Huong K.H., Sevakumaran V., & Amirul A.A., (2021). P(3HB-co-4HB) as high value polyhydroxyalkanoate: its development over recent decades and current advances. Crit. Rev. Biotechnol., 41, 474-490.

[5] Kim, J., Pahari, S., Shah, P., & Kwon, J.S.-I., (2023). Enhanced Polyhydroxyalkanoate (PHA) Production through Multiscale Modeling and Process Control Strategies: A Novel Approach to Bio-Based Polymer Synthesis. In 2023 AIChE Annual Meeting. AIChE.

[6] McAdam B., Fournet M.B., McDonald P., & Mojicevic M., (2020). Production of Polyhydroxybutyrate (PHB) and factors impacting its chemical and mechanical characteristics. Polymers, 12, 2908.