Idania Valdez-Vazquez

History of adaptation determines short‐term shifts in performance and community structure of hydrogen‐producing microbial communities degrading wheat straw

This study addresses the question of ecological interest for the determination of structure and diversity of microbial communities that degrade lignocellulosic biomasses to produce biofuels. Two microbial consortia with different history, native of wheat straw (NWS) and from a methanogenic digester (MD) fed with cow manure, were contrasted in terms of hydrogen performance, substrate disintegration and microbial diversity. NWS outperformed the hydrogen production rate of MD. Microscopic images revealed that NWS acted on the cuticle and epidermis, generating cellulose strands with high crystallinity, while MD degraded deeper layers, equally affecting all polysaccharides. The bacterial composition markedly differed according to the inocula origin. NWS almost solely comprised hydrogen producers of the phyla Firmicutes and Proteobacteria, with 38% members of Enterococcus. After hydrogen fermentation, NWS comprised 8% Syntrophococcus, an acetogen that cleaves aryl ethers of constituent groups on the aromatic components of lignin. Conversely, MD comprised thirteen phyla, primarily including Firmicutes with H2‐producing members, and Bacteroidetes with non‐H2‐producing members, which reduced the hydrogen performance. Overall, the results of this study provide clear evidence that the history of adaptation of NWS enhanced the hydrogen performance from untreated wheat straw. Further, native wheat straw communities have the potential to refine cellulose fibers and produce biofuels simultaneously.

Microscopy Applied In Biomass Characterization

This chapter serves as an introduction to the major types of microscopy that are applied to the characterization of lignocellulosic biomasses. The covered techniques include optical microscopies (light, Raman, and confocal microscopy), scanning probe microscopy, and electron microscopy. This chapter provides a general description of the principles, advantages and drawbacks, type of information that can be obtained using the different microscopic techniques, and includes a wide range of examples on the use of such techniques to characterize lignocellulosic biomass samples before and after pretreatments. Finally, some of the reviewed microscopic techniques were used to visualize samples of wheat straw nodes before and after acid and alkali pretreatments. This chapter is designed to help scientists select the best microscopic technique to study biomass feedstocks with recalcitrant natures.