Microbial biotechnology has transformed industrial production by leveraging microbes as versatile biofactories, driving advancements in both productivity and sustainability. This chapter examines recent progress in engineered microbial systems, including Escherichia coli, yeast, mammalian, insect, and plant cells, for synthesising high-value products such as antibiotics, biopolymers, and therapeutic compounds (e.g. anti-HIV, anti-cancer, anti-fungal, and anti-inflammatory agents). It also explores their applications in biosensors for pathogen detection and environmental monitoring (e.g. metabolites and metal ions) and their role in biorefineries for sustainable biofuel and chemical production from biomass. Further, the chapter highlights how synthetic biology and metabolic engineering provide efficient, eco-friendly alternatives to traditional chemical synthesis. By integrating these innovations, microbial biotechnology presents a powerful solution to industrial and biomedical challenges.