Production of Citric Acid (A. Niger)

3680 Words Feb 27th, 2013 15 Pages
Part B

Small Scale Literature Review

Running Head: Factors Affecting Citric Acid Production by Aspergillus niger

Factors Affecting Citric Acid Production by Aspergillus niger

Ong Chia Swing, Student.

Nilai University

1. Introduction

Citric acid is a natural preservative or conservative that is used to add an acidic, sour taste to foods and beverages. In the context of biochemistry, the conjugate base of citric acid which is the citrate plays an important role as an intermediate in the citric acid cycle which occurs in the metabolism of all aerobic organisms. Due to its importance to most organisms, more than a million tonnes are produced every year via fermentation. It is used mainly as an acidifier, flavouring and as a chelating
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2.2 Effects of Sucrose Concentration during Citric Acid Accumulation by A. niger

Next, a research paper by Aysegul and Christian (2001), a study where it focused on the effects of sucrose concentration during citric acid accumulation by Aspergillus niger. It was hypothesised that different levels of sucrose concentration can determine the regulation of the citric acid production rate. Due to its regulation, the metabolism took place at several levels including the control of gene expression, translational control, control of enzyme activity and control through the spatial distribution of enzymes (Panneman et al., 1996; Kubicek et al., 1977 & 1978; Wolschek et al., 1996; Visser et al., 1992). Therefore, a number of the enzymes involved in hexose utilisation are regulated as well by inhibitors, activators and protein phosphorylation or dephosphorylation. It is believed that the citric accumulation is known to be stimulated by high sugar concentration suggesting it may be influenced by osmotic stress. The main goal of this research paper was to investigate the phosphorylated proteins produced during the osmotic stress conditions due to high sucrose concentrations as the possible role of protein phosphorylation due to osmotic stress has not been investigated in Aspergillus niger ATCC 11414 under citric acid production conditions in the past. Basically, an increase in citric acid accumulation with increasing concentrations of sugar is not surprising as it may simply
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