Unraveling Mechanisms behind Biomass-Clay Interactions Using Comprehensive Multiphase Nuclear Magnetic Resonance (NMR) Spectroscopy

Abstract

The interactions of the different components of soils, such as living biomass and organic matter, with mineral surfaces are of considerable interest due to their environmental reactivity and potential for improving carbon storage in the long-term. Also, microbial species are known to participate in key soil processes, and it has been hypothesized that microbes do not just sorb to minerals but also actively bind to minerals and may even play an important role in mineral formation. Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful tools to study the structure and association in complex samples. A new NMR technique, referred to as comprehensive multiphase (CMP) NMR spectroscopy, has been applied to analyze unaltered samples in novel NMR experiments to study structures and interactions in situ. In this research, we use CMP-NMR to study biomass-clay interactions in laboratory-generated biomass-clay complexes. CMP-NMR analyses showed that fungal biomass associates with clay mainly via aliphatic functional groups, while carbohydrates dominate at the clay-water interface. The results for bacterial cells suggest the formation of a biofilm that attached non-specifically to clay surfaces. This is the first time that a molecular approach of whole-cell attachment to clay in biomass-clay complexes is obtained with this technique. This in-depth molecular information provides a unique insight into the binding mechanisms between biomass and clay minerals. This novel information can improve the fundamental understanding of soil organic matter formation and stabilization processes involved in soil formation, as well as the role of the mineral fraction of whole soils in biomass/organic matter protection or the preferential binding of pollutants.