Continuous production of citric acid by immobilized whole cells of Aspergillus niger.

Abstract

A process of continuous citric acid production from sugarcane molasses by fermentation with immobilized whole cells of A. niger KCU 520 is described. Both calcium alginate beads and polyacrylamide gel (PAG) slab entrapment methods were used for immobilization of cells. The optimum fermentation conditions for citric acid fermentation by immobilized cells were sugars, 10%; pH, 4.0; inoculum size, 20%, and temperature, 32-35°C. With calcium-alginate and PAG-immobilized cells, an overall citric acid production rate of 8.5 g and 12.0 g///day (9.3% and 12% sugar conversion to citric acid per day), respectively was achieved in a single-stage bioreactor. When the PAG-immobilized cells were used in a two-stage bioreactor, approximately 20.0 g citric acid/ l /day (20% sugar conversion to citric acid per day) was produced and the PAG-immobilized cells were continuously used for at least 20 days without any significant loss of productivity.Recently, immobilized biocatalyst technology has rapidly emerged as a novel means to utilize enzymes and whole cells as efficient and heterogeneous catalyst for a multitude of industrial and medical applications (1,4,7,15). Immobilization of living organism is found to be more advantageous than immobilization of enzymes as in situ regeneration of activity is merely by supplementing suitable nutrients (5). In addition, whole metabolic pathway of microbe or part of it required for the production of a particular compound, can be efficiently used over a longer period under immobilized state.A number of organic acids are produced by moulds, and citric acid is one of the most important metabolic products, now produced almost exclusively by fermentation, using selected strains of A. niger (2,18). Although much work has

Influence of alcohols on citric acid production by Aspergillus niger A-9 entrapped in polyacrylamide gels

“…Many studies have been carried out, mainly on the production of organic acid (Eikmeier & Rehm, 1984;Fujii, Yasuda, & Sakahibara, 1994;Sankpal, Joshi, & Kulkarni, 2001;Sankpal & Kulkarni, 2002), enzymes and oligosaccharides, using mycelia immobilized on various support materials by entrapment or adsorption techniques. With respect to citric acid production, significant studies have been carried out to achieve higher volumetric productivities under conditions of submerged and surface modes of growth (Eikmeier & Rehm, 1987;Garg & Sharma, 1992).…”

Continuous production of citric acid from sugarcane molasses using a combination of submerged immobilized and surface stabilized cultures of Aspergillus niger KCU 520

“…2A kgM-3h -I) and citric acid product concentration in the effluent (110 kg M -3) than figures from repeated batch or semicontinuous processes using either surface (Garg and Sharma, 1991) or immobilized cultures of Aspergillus niger KCU 520 (Garg and Sharma, 1992 production reported here appears to be quite promising and has the potential of being developed into an industrial process.…”

“…In recent years citric acid has also been produced on a laboratory scale with Aspergillus niger cells immobilized on calcium alginate gel (Vaija, et al 1982;Rehm, 1984, 1987a;Vaija and Linko, 1986;Honecker, et al 1989), polyacrylamide gel (Horitsu, eta]. 1985; Garg and Sharma, 1992), and on polyurethane foam (Lee, et al, 1989;Vassilev and Vassileva, 1990). In addition, Kautola, et al (1991a) and Rymowicz, et al (1993) Aspergillus niger (Garg and Sharma, 1991) was used in this study.…”

“…The spo~es ~ere aseptically harvested in sterile distilled water (i0 -I0 spores/ml) and immobilized by e,,trapmenL Jn Ca-alginate beads of 7mm diameter as described previously (Garg and Sharma, 1992). Each bead contained about 2 x I0 ~ spores.…”

Modeling and control of dissolved oxygen concentration in the fermentation of Glucose to Gluconic Acid

“…Among these methods, producing gluconic acid with Aspergillus niger microbe is preferable due to the easier isolation of the product compared to other biocatalysts. Such isolation could be carried out by flocculation with polyelectrolytes (Lee and Long, [10]), covalent binding to a glycidyl ester copolymer (Nelson,[15]), entrapment in gels (Garg and Sharma, [6]) and adsorption onto supports (Heinrich and Rehm, [7]; Sakurai et al, [21]; Fujii et al, [5]). On the other hand, producing gluconic acid from glucose using metal catalysts, regardless of the high conversion and selectivity, creates its own problem of catalyst deactivation, which is caused by self-poisoning and overoxidation (Nikov and Paev, [16]).…”