Application of airlift gas-liquid-solid reactors in biotechnology

Abstract

Airlift reactors are pneumatically agitated reactors with circulation in a defined cyclic pattern through a loop of conduits. The possibility of providing the required aeration and agitation during fermentation processes, with low energy input, has brought a flourishing of industrial interest in airlift reactors. Due to the mildness and uniformity of turbulence in airlift reactors compared to conventional reactors, such as stirred tank reactors and bubble columns, particular interest is being focused on airlift reactors for use with various cell cultures. This paper presents an overview of the current state of knowledge in airlift reactor design and operation with a focus on external-loop airlift reactors. Emphasis is placed on a discussion of macroscale liquid circulation velocity because it is this parameter which distinguishes airlift reactors from other pneumatically agitated reactors, such as bubble columns. In addition, specific areas where gaps presently exist in the knowledge of airlift reactor design, operation, and scale-up are identified and recommendations are made for future research.