Genetically encoded biosensor systems operating in living
cells
are versatile, cheap, and transferable tools for the detection and
quantification of a broad range of small molecules. This review presents
state-of-the-art biosensor designs and assemblies, featuring transcription
factor-, riboswitch-, and enzyme-coupled devices, highly engineered
fluorescent probes, and emerging two-component systems. Importantly,
(bioinformatic-assisted) strategies to resolve contextual issues,
which cause biosensors to miss performance criteriain vivo, are highlighted. The optimized biosensing circuits can be used
to monitor chemicals of low molecular mass (<200 g mol–1) and physicochemical properties that challenge conventional chromatographical
methods with high sensitivity. Examples herein include but are not
limited to formaldehyde, formate, and pyruvate as immediate products
from (synthetic) pathways for the fixation of carbon dioxide (CO2), industrially important derivatives like small- and medium-chain
fatty acids and biofuels, as well as environmental toxins such as
heavy metals or reactive oxygen and nitrogen species. Lastly, this
review showcases biosensors capable of assessing the biosynthesis
of platform chemicals from renewable resources, the enzymatic degradation
of plastic waste, or the bioadsorption of highly toxic chemicals from
the environment. These applications offer new biosensor-based manufacturing,
recycling, and remediation strategies to tackle current and future
environmental and socioeconomic challenges including the wastage of
fossil fuels, the emission of greenhouse gases like CO2, and the pollution imposed on ecosystems and human health.