Acidic pre-treatment of sugarcane molasses for citric acid production by Aspergillus niger NG-4

Citric acid obtained through the microbial fermentation is considered synthetic while that of present in fruits is referred to as natural (Ranya et al., 1999; Karklins et al., 2001). It is responsible for the tart taste of various fruits e.g., lemons, limes, oranges, pineapples, pears and gooseberries. It can be extracted from the citrus fruit juice by adding calcium oxide to form calcium citrate followed by recovery through the addition of sulphuric acid (Bizek et al., 1992; Karklins et al., 1996; Honda et al., 2011). It is one of the most important bulk-produced organic acids (Wieizorek and Brauer, 1998; Vanags and Viesturs, 2001). It is non-toxic and easily oxidized in the human body (Ma 2000). It can be used industrially for food, confectionary, beverages, to flavour the drinks, jam, jellie and pharmaceuticals. Its uses depend on three properties acidity flavour and salt formation. It adjusts the pH and chelates the trace metals. These and many other uses have placed greater stress on increasing the citric acid production (Kato et al., 1999). The worldwide demand for citric acid is about 6.0×10 tons per year (Karaffa and Kubicek, 2003). Citric acid has been produced on industrial scale by the fermentation of carbohydrates, initially exclusively by A. niger but in recent times ISSN: 2319-7706 Volume 4 Number 6 (2015) pp. 584-595 http://www.ijcmas.com