I'm new in the area of plant secondary metabolism. So i wanted to know if there is any way to genetically express some specific secondary metabolites (Alkaloids, Terpenes, etc) on diferent microorganisms (Bacteria, yeasts, microalgae).
Yes you can use against microbes against disease causing bacteria if it give activity then u can check on animal model so, you can get idea about its toxicity.
i saw one study about vanilla. they take vanillin gennes from vanilla plant to production vanillin by bacteria. also, there is rebodiosides. some GDO yiest and bacteria secreting ribodioside a and b agains to stevia.
Attached is a Review paper (2015) titled "Engineering of Secondary Metabolism". In the paper, it discusses the methods and challenges of using microbes (such as E. Coli) for producing plant secondary metabolites (yellow highlights).
For evaluation of the Minimum Inhibitory Concentration (MIC) from plant extracts, this attached paper has detail description. Hopefully, it is useful to you.