The diversity of plant carbohydrate hydrolysis in nature and technology

Plant carbohydrate hydrolysis is a vital process for Earth's stability. Photosynthesis drives carbon accumulation by synthesizing carbohydrate polymers such as starches and cell wall polysaccharides. The resulting biomass feeds the food chains, which closes the carbon cycle on the planet. A diversity of hydrolysis mechanisms evolved—apparently independently—in plants, microorganisms, and animals. These organisms hydrolyze polymers to their elementary units (monosaccharides), which are metabolized for energy production and the construction of living bodies. Plants can also hydrolyze their carbohydrates. Sucrose, raffinose, fructans, starch, and several cell wall polymers can be substrates to plant hydrolases. In some cases, these carbohydrates serve as reserves (short- or long-term). In others, developmental processes (e.g., abscission of leaves and flowers, fruit ripening, aerenchyma formation) involve hydrolysis of part of the cell walls. This chapter reviews hydrolysis's main mechanisms and discusses the integration, evolution, and importance of this process for biotechnology and life maintenance on Earth.