Abstract

Propionic acid (PA) is a carboxylic acid applied in a variety of processes, such as food and feed preservative, and as a chemical intermediate in the production of polymers, pesticides and drugs. PA production is predominantly performed by petrochemical routes, but environmental issues are making it necessary to use sustainable processes based on renewable materials. PA production by fermentation with the Propionibacterium genus is a promising option in this scenario, due to the ability of this genus to consume a variety of renewable carbon sources with higher productivity than other native microorganisms. However, Propionibacterium fermentation processes present important challenges that must be faced to make this route competitive, such as: a high fermentation time, product inhibition and low PA final titer, which increase the cost of product recovery. This article summarizes the state of the art regarding strategies to improve PA production by fermentation with the Propionibacterium genus. Firstly, strategies associated with environmental fermentation conditions and nutrition requirements are discussed. Subsequently, advantages and disadvantages of various strategies proposed to improve process performance (high cell concentration by immobilization or recycle, co-culture fermentation, genome shuffling, evolutive and metabolic engineering, and in situ recovery) are evaluated.

摘要

丙酸 (PA) 是一种应用于多种工艺的羧酸，例如食品和饲料防腐剂，以及作为生产聚合物、农药和药物的化学中间体。PA 生产主要通过石化路线进行，但环境问题使得有必要使用基于可再生材料的可持续工艺。在这种情况下，通过丙酸杆菌属发酵生产 PA是一个很有前途的选择，因为该属能够消耗各种可再生碳源，并且生产率高于其他本地微生物。然而，丙酸杆菌发酵过程提出了使这条路线具有竞争力所必须面对的重要挑战，例如：发酵时间长、产物抑制和 PA 最终滴度低，这些都会增加产品回收的成本。本文总结了有关通过丙酸杆菌属发酵提高 PA 生产的策略的最新技术水平。首先，讨论了与环境发酵条件和营养要求相关的策略。随后，评估了为提高工艺性能而提出的各种策略的优缺点（通过固定或再循环的高细胞浓度、共培养发酵、基因组改组、进化和代谢工程以及原位恢复）。