Enhanced polyhydroxyalkanoate production from organic wastes via process control.

Area of Science:

• Biotechnology and Bioengineering
• Environmental Engineering
• Process Control

Background:

• Polyhydroxyalkanoates (PHAs) are biodegradable polymers with significant potential for sustainable plastic alternatives.
• Mixed microbial cultures offer a cost-effective route for PHA production from waste streams.
• Optimizing control strategies is crucial for enhancing PHA yield and productivity in bioreactors.

Purpose of the Study:

• To develop and evaluate a model-based control scheme for improving polyhydroxyalkanoate (PHA) production efficiency.
• To determine optimal operational parameters, including dissolved oxygen (DO) set-point and initial substrate concentration.
• To compare the performance of the proposed feedback control strategy against a simpler empirical algorithm.

Main Methods:

• Implementation of a model-based controller for pulsed substrate addition and dissolved oxygen (DO) regulation.
• Dynamic mathematical modeling to predict optimal substrate pulse intervals.
• Bench-scale experimental validation to determine optimal DO set-point and initial substrate concentration.
• Comparative analysis of the proposed control strategy versus an empirical algorithm.

Main Results:

• Achieved a high substrate conversion rate of 1.370±0.598 mg PHA/mg COD/d.
• The model-based control strategy demonstrated superior performance compared to the empirical algorithm.
• Successfully identified PHA saturation points, with maximum PHA content reaching 71.0±7.2 wt.%.
• The controller effectively predicted the optimal timing for subsequent substrate additions.

Conclusions:

• Model-based control is a highly effective strategy for enhancing PHA productivity in mixed-culture systems.
• Optimized DO levels and substrate feeding strategies are critical for maximizing PHA accumulation.
• The developed control approach offers a robust method for industrial-scale PHA bioproduction and process optimization.