bloom dynamics depend principally on the impact of consumers, a long-recognized control of phytoplankton abundance (30). Our findings for Synechococcus agree with those of Behrenfeld and Boss in so far as division rates (and, by inference, loss rates) are roughly 10 times the accumulation (net growth) rates. Our results differ, however, in that we find a significant positive correlation between division and accumulation rates over the course of the spring bloom (Fig. 4, B and C). This correlation was not detected by Behrenfeld and Boss, and perhaps should not be expected to be evident in the satellite-based observations of chlorophyll concentration that they analyzed (29). Those observations aggregate the entire phytoplankton community over a relatively large region of the ocean and mask individual responses of different taxa.Our observations, made at a much smaller spatial scale and with much finer taxonomic and temporal resolution than that of satellite data, reveal a connection between division rates and the bloom dynamics of Synechococcus. Consumers (including grazers, viruses, and parasites) certainly play a major role in shaping the bloom's trajectory, but the bloom is triggered by an environmental factor, the seasonal temperature rise, which leads to increases in the Synechococcus division rate (Fig. 3). The bloom persists until the division rate plateaus (Fig. 4B), at which point losses overtake division and the bloom begins to decline.We were able to diagnose the importance of temperature in regulating the dynamics of a ubiquitous marine primary producer, Synechococcus, by exploiting a 13-year time series comprising data on millions of individual cells and their traits. This allowed us to not only quantify the relationship between temperature and cell division in a natural population, but also to document how that relationship is the basis for a dramatic phenological shift affecting both Synechococcus and their consumers. It remains to be seen whether this ecological coupling will hold as warming trends continue in the decades to come.

A central feature of most lignocellulosic-biomass-valorization strategies is the depolymerization of all its three major constituents: cellulose and hemicellulose to simple sugars, and lignin to phenolic monomers. However, reactive intermediates, generally resulting from dehydration reactions, can participate in undesirable condensation pathways during biomass deconstruction, which have posed fundamental challenges to commercial biomass valorization. Thus, new strategies specifically aim to suppress condensations of reactive intermediates, either avoiding their formation by functionalizing the native structure or intermediates or selectively transforming these intermediates into stable derivatives. These strategies have provided unforeseen upgrading pathways, products and process solutions. In this Review , we outline the molecular driving forces that shape the deconstruction landscape and describe the strategies for chemical functionalization. We then offer an outlook on further developments and the potential of these strategies to sustainably produce renewable-platform chemicals.

Here we report that γ-valerolactone (GVL), a biomass-derived solvent, can be used to facilitate the mild pretreatment of lignocellulosic biomass. An 80% GVL, 20% water solvent system was used to pretreat hardwood at the mild temperature of 120°C with an acid loading of 75 mM H 2 SO 4 . Up to 80% of original lignin was removed with 96-99% of original cellulose retained in the pretreated substrates. The use of a mild temperature and low acid concentrations caused negligible degradation of sugars. Up to 99% of the original glucan and 96% of the original xylan could be recovered after pretreatment. The pretreated substrate was quantitatively converted to sugars (99% and 100% total glucose and xylose yield) with an enzyme loading of 15 FPU g −1 glucan. These digestibilities were three times higher than those obtained when using other organic solvents such as tetrahydrofuran or ethanol, and 20 times higher than when pure water was used during pretreatment. Over 99.5% of GVL could be recovered by liquid-CO 2 extraction of the pretreated slurries while removing less than 1% of the sugars. This approach produced pretreatment slurries that could easily undergo high-solids (30% w/v) enzymatic hydrolysis without any substrate washing or drying. We obtained glucose and xylose yields of up to 90% and 97%, respectively, and generated sugar streams with sugar concentrations up to 182 g L −1 .The sugar-based biorefinery platform has been increasingly studied for the purpose of sustainably producing chemicals, fuels and materials from lignocellulosic biomass.

Lignin is one of the most promising sources of renewable aromatic hydrocarbons. Current methods for its extraction from lignocellulosic biomass-which include the kraft, sulfite, and organosolv processes-result in the rapid formation of carbon-carbon bonds, leading to a condensed lignin that cannot be effectively depolymerized into its constituent monomers. Treatment of lignocellulosic biomass with aldehydes during lignin extraction generates an aldehyde-stabilized lignin that is uncondensed and can be converted into its monomers at near-theoretical yields. Here, we outline an efficient, reproducible, and scalable process for extracting and purifying this aldehyde-stabilized lignin as a solid, which can easily be re-dissolved in an organic solvent. Upon exposure to hydrogenolysis conditions, this material provides near-theoretical yields of aromatic monomers (~40-50% of the Klason lignin for a typical hardwood). Cellulose and hemicellulose are also efficiently fractionated. This protocol requires 6-7 h for the extraction of the stabilized lignin and a basic proficiency in synthetic chemistry.