An Integrated Strategy For Recovery And Purification Of Poly-Gamma-Glutamic Acid From Fermentation Broth And Its Techno-Economic Analysis

Poly-gamma-glutamic acid (PGA) is a biopolymer with great application prospects and developmental value and which can be produced via microbial fermentation. However, due to the high viscosity of fermentation broth, the recovery and purification of PGA constitute bottlenecks that may limit its use. In this study, an integrated strategy for the recovery and purification of PGA from fermentation broth was developed. Unlike the previously reported ethanol or copper sulfate precipitation strategy, the approach developed in this study includes four unit operations: acidification, plate and frame filtration, cyclic ultrafiltration, and freeze-drying. The strategy does not require the use of any exogenous precipitant, which simplifies the process, lowers costs, and better protects the environment. After optimizing each unit operation, a light yellow powdered PGA was obtained and characterized; its recovery rate, purity, and molecular weight were 55%, 94.8%, and 3,020-5,150 kDa, respectively. Furthermore, the process design and techno-economic analyses were performed at an annual output level of 50 metric tons PGA using SuperPro Designer. A production cost of $105.58/kg and payback period of 1.55 years were achieved. This study provides an economically feasible strategy for the recovery and purification of high molecular-weight PGA from fermentation broth at an industrial scale.