Agricultural Wastes: A Feedstock for Citric Acid Production Through Microbial Pathway

Abstract

Citric acid holds a dominant position in industrial manufacturing due to its widespread application. It can be extricated as natural products through microbial pathways. A greater part of citric acid production is currently achieved by fermentation techniques where molasses/starch-based media are used. Microbial strains such as Penicillium spp, Aspergillus spp, Acremonium spp, and many others excrete variable amounts of citric acid as a primary metabolite. So far, Aspergillus niger has been recognized to produce a higher yield of around 112 g of citric acid /100 g of sucrose. However, the increasing demands has necessiated the need for more efficient procedures to enhance the yield. Several studies have been documented where agri-wastes such as rice straw, coconut husk, corn stalk, apple pomace, sugarcane bagasse, and many others were subjected to varied microorganisms (mainly fungal species) to increase the productivity of citric acid. Substantial citric acids have been produced using genetically modifying organisms (fungi Aspergillus and yeast Candida) and divergent combinations of microbe-substrate, but large-scale production has not yet been established. Also, the utilization of these fossil carbon sources has caused environmental deterioration, which instigates interest in agricultural waste as a potential substrate. Agricultural wastes are considered an economically feasible option and a renewable source that can be consumed by plenty of microorganisms. This chapter covers a detailed description of agri-waste bioconversion to citric acid which can further help in this fast-moving domain. � 2023 selection and editorial matter Gustavo Molina, Minaxi Sharma, Vipin Chandra Kalia, Franciele Maria Pelissari, Vijai Kumar Gupta, individual chapters, the contributors.