Construction of a Simple Multipurpose Airlift Bioreactor and its Application for Yeast Propagation and Amylase Production

Abstract

Nigeria and other developing countries have abundant biomass resources that can be converted to many value-added products. However, these biomass resources are usually exported un-processed at very low prices because of lack of appropriate technology for processing. One of such limitations is lack of simple bioreactors for large scale cultivation of cells. The conventional bioreactors are usually very complex, expensive and require constant power supply for mixing and agitation. They are therefore not suitable for developing countries where electricity supply is very unsteady. The aim of the present research is to develop a simple airlift bioreactor which can be operated even without electricity supply. The bioreactor was constructed of acrylic panels and demarcated into a riser and a down comer chambers. The total volume of the bioreactor was 3.9 L with a working volume of 3.0 L. Mixing was achieved by aeration using mechanically operated gasoline-powered air compressor. Mixing efficiency and thus dissolved oxygen concentrations can be controlled by adjusting the aeration rate. The efficacy of the bioreactor was demonstrated by cultivation of facultative aerobic microorganism (Saccharomyces cerevisae) and aerobic microorganism (Aspergillus awamori). At both low sugar concentration (50 g/L) and high sugar concentration (100 g/L), the growth rates and thus the final concentrations of Saccharomyces cerevisae biomass were higher in the bioreactor than in Erlenmeyer flasks. Also in comparison with flask cultures, cultivation of Aspergillus awamori in the bioreactor resulted in higher gluco-amylase and α-amylase activities.

Key Words: Bioreactor, Aerobic microorganism, Acrylic panels, Aspergillus awamori