Fuente: Broccoli Byproducts Extraction A new field of biotechnological research is the application of waste materials for the fermented microbial synthesis of organic acids, which is motivated by the demand for economical and environmentally friendly production techniques. Lactic acid, succinic acid, citric acid, and acetic acid are examples of organic acids varieties, those are used as crucial industrial intermediates in chemicals, food, pharmaceuticals, and biodegradable plastics. These organic acids have traditionally been produced using petrochemical or food-grade sugars, but the increasing need for sustainable alternatives has raised interest in using waste biomass and byproducts as the initial ingredients for fermentation processes. Microbial fermentation of waste materials, including food waste, lignocellulosic biomass, industrial byproducts, and agricultural residues, offers a low-cost feedstock for the synthesis of organic acid while also posing a threat to the environment. Under ideal fermentation circumstances, different types of microorganisms, yeast, bacteria including fungi, transform complicated waste materials into valuable organic acids. The waste resource's high protein, carbohydrate, and lignocellulose content necessitates the careful selection of microbial strains with particular enzymatic capabilities for effective fermentation and breakdown. This book chapter examines the latest developments in the microbial fermentation of waste materials to produce organic acid, emphasizing important microbes, metabolic processes, and fermentation methods. The potential advantages of this strategy, such as lower costs, less waste, and a more sustainable environment, highlight its potential as a crucial technology for upcoming bio-based industrial production.