Poly-γ-glutamic acid is a biopolymer with wide applications in food, cosmetic and pharmaceutical industries. Currently, PGA is produced by Bacillus spp. in batch stirred-tank fermentation and the product is recovered and purified through alcohol precipitation. Current commercial production processes are limited by several critical problems, including poor mass transfer due to the high broth viscosity, difficult downstream processing with cell-containing media, and costly purification process using a large amount of alcohol. In this work, a novel economic process consisting of a rotating fibrous bed bioreactor for cell immobilization and fermentation and a ultrafiltration process for concentrating the biopolymer solution before alcohol precipitation was developed to produce a concentrated cell-free PGA broth that can be readily recovered and purified with alcohol precipitation at a lower cost. Several process parameters affecting the fermentation and ultrafiltration have been studied and optimized, and the results will be discussed in this paper.

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