Full Length Research Paper

Use of nitrous acid mutant of Aspergillus niger for citric acid production from local cane-molasses

Kabera Justin¹, Ugirinshuti Viateur1 and Mukantirenganya Prudentienne^2*

[1]Researcher at Institute of Scientific and Technological Research, Musanze station, Ruhengeri city, Rwanda.

2Rubavu city, Western Province, Rwanda.

*Corresponding author. E-mail: pmukantirenganya@yahoo.fr. Tel: + (250)783418797. Fax:+ (250) 546500.

Accepted 24 June, 2010

   Abstract

In this study, the enhancement of citric acid production from local molasses was attempted by mutagenesis. A local stain of Aspergillus niger was isolated from lemon leaves and treated with nitrous acid. The obtained mutant and the wild type of A. niger were separately used for the bioconversion of the local molasses into citric acid. The molasses fermentation was carried out at 30°C in a stirred flask. The results showed that the mutant exhibited an increased efficiency for citric acid production when compared with the wild type. It produced 230.45 gl^-1 of citric acid; two fold increase over the parent strain (105.67 gl^-1), with higher sugar consumption by the mutant compared with the wild type. The maximum citric acid production levels were reached on the 9th day of fermentation by the mutant and the 10th day of fermentation by the wild strain. The mutant proved to be appropriate for citric acid production and waste material valorization in Rwanda. Also, this investigation showed itself to be one of ecofriendly technologies for Rwanda. So, the use of this technology should have impact on both the Rwanda economic development and environmental protection.

Key words: Rwanda, Aspergillus niger, bioconversion, cane-molasses, citric acid, mutagenesis, mutant, nitrous acid.