Carbohydrates, which include small compounds (sugars) as well as complex biopolymers (cellulose, starch), are intimately involved in the cycling of water and nutrient fluxes in environmental matrices. Secretions of carbohydrates are implicated in the retention of hydrated soil nanopores near plant roots and microbial cells despite severe dryness in the bulk soil. The microbial processing of carbohydrates is important both in natural carbon cycling and in engineered waste conversion to biofuels. My research group combines experimental techniques with theoretical simulations to unravel the underlying chemical and biochemical mechanisms in these processes. This presentation will highlight two main research efforts, which have led to novel insights into the role of carbohydrates in the trapping of water within mineral nanopores and in the selective bacterial conversion of cellulosic wastes to biofuel products. These insights advance our understanding on how to predict these natural bioenvironmental processes and to exploit them for engineered purposes.