This document discusses strain improvement for industrial microbes. It defines strains as genetic variants of microorganisms and industrial strains as those that synthesize a main product to simplify production. Strain development is important for efficient bioprocesses as it enhances microbial biosynthesis of desired products at high titers. Methods of strain improvement discussed include mutation, recombination techniques like transduction and transformation, and recombinant DNA technology like genetic engineering to alter microbial genetics.