We developed a new system to improve the overproduction of soluble proteins in based on a plasmid encoding the small heat-shock protein, Lo18, derived from the lactic acid bacterium . The efficiency of this system was compared with that of another system based on production of the universal chaperone GroEL/ES. A compatible plasmid encoding beta-glucosidase was constructed for the overproduction and aggregation of this enzyme. Co-expression with Lo18 resulted in an increase in soluble beta-glucosidase levels similar to that obtained in the GroEL/ES co-expression system. Lo18 was found preferentially in the insoluble fraction, associated with aggregated enzyme. By contrast, GroEL/ES was more abundant in the soluble fraction.