Dyoni Matias de Oliveira

The acetyl bromide method is faster, simpler and presents best recovery of lignin in different herbaceous tissues than Klason and thioglycolic acid methods.

We compared the amount of lignin as determined by the three most traditional methods for lignin measurement in three tissues (sugarcane bagasse, soybean roots and soybean seed coat) contrasting for lignin amount and composition. Although all methods presented high reproducibility, major inconsistencies among them were found. The amount of lignin determined by thioglycolic acid method was severely lower than that provided by the other methods (up to 95%) in all tissues analyzed. Klason method was quite similar to acetyl bromide in tissues containing higher amounts of lignin, but presented lower recovery of lignin in the less lignified tissue. To investigate the causes of the inconsistencies observed, we determined the monomer composition of all plant materials, but found no correlation. We found that the low recovery of lignin presented by the thioglycolic acid method were due losses of lignin in the residues disposed throughout the procedures. The production of furfurals by acetyl bromide method does not explain the differences observed. The acetyl bromide method is the simplest and fastest among the methods evaluated presenting similar or best recovery of lignin in all the tissues assessed.

Ferulic acid: a key component in grass lignocellulose recalcitrance to hydrolysis

In the near future, grasses must provide most of the biomass for the production of renewable fuels. However, grass cell walls are characterized by a large quantity of hydroxycinnamic acids such as ferulic and p-coumaric acids, which are thought to reduce the biomass saccharification. Ferulic acid (FA) binds to lignin, polysaccharides and structural proteins of grass cell walls cross-linking these components. A controlled reduction of FA level or of FA cross-linkages in plants of industrial interest can improve the production of cellulosic ethanol. Here, we review the biosynthesis and roles of FA in cell wall architecture and in grass biomass recalcitrance to enzyme hydrolysis.

Increased Gibberellins and Light Levels Promotes Cell Wall Thickness and Enhance Lignin Deposition in Xylem Fibers

Light intensity and hormones (gibberellins; GAs) alter plant growth and development. A fine regulation triggered by light and GAs induces changes in stem cell walls (CW). Cross-talk between light-stimulated and GAs-induced processes as well as the phenolic compounds metabolism leads to modifications in lignin formation and deposition on cell walls. How these factors (light and GAs) promote changes in lignin content and composition. In addition, structural changes were evaluated in the stem anatomy of tobacco plants. GA3 was sprayed onto the leaves and paclobutrazol (PAC), a GA biosynthesis inhibitor, via soil, at different irradiance levels. Fluorescence microscopy techniques were applied to detect lignin, and electron microscopy (SEM and TEM) was used to obtain details on cell wall structure. Furthermore, determination of total lignin and monomer contents were analyzed. Both light and GAs induces increased lignin content and CW thickening as well as greater number of fiber-like cells but not tracheary elements. The assays demonstrate that light exerts a role in lignification under GA3 supplementation. In addition, the existence of an exclusive response mechanism to light was detected, that GAs are not able to replace.

Lignin-induced growth inhibition in soybean exposed to iron oxide nanoparticles

Plants are occasionally exposed to environmental perturbations that limit their growth. One of these perturbations is the exposure to and interaction with various nanoparticles (NPs) that are discarded continuously into the environment. Hitherto, no study has been carried out evaluating the effects of iron oxide (γ-Fe2O3) NPs on soybean growth and lignin formation, as proposed herein. For comparative purposes, we also submitted soybean plants to non-nanoparticulate iron (FeCl3). Exposure of the plants to γ-Fe2O3 NPs increased cell wall-bound peroxidase (POD) activity but decreased phenylalanine ammonia lyase (PAL) activity due, probably, to the negative feedback of accumulated phenolic compounds. In contrast, FeCl3 decreased cell wall-bound POD activity. Both γ-Fe2O3 NPs and FeCl3 increased the lignin content of roots and stems. However, significant lignin-induced growth inhibition was noted only in stems after exposure to NPs, possibly due to changes in lignin monomer composition. In this case, γ-Fe2O3 NPs decreased the guaiacyl monomer content of roots but increased that of stems. The high levels of monomer guaiacyl in stems resulting from the action of γ-Fe2O3 NPs decreased syringyl/guaiacyl ratios, generating more highly cross-linked lignin followed by the stiffening of the cell wall and growth inhibition. In contrast, FeCl3 increased the contents of monomers p-hydroxyphenyl and syringyl in roots. The observed increase in the syringyl/guaiacyl ratio in plant roots submitted to FeCl3 agrees with the lack of effect on growth, due to the formation of a less condensed lignin. In brief, we here describe that γ-Fe2O3 NPs and FeCl3 act differently in soybean plants.

Ten Simple Rules for Developing a Successful Research Proposal in Brazil

Writing well is fundamental to publishing and having a successful scientific career [1], and being able to write a good research proposal is critical for obtaining financial support [2]. In emerging economies, such as Brazil, it is necessary to confront drawbacks not encountered in high-income countries [3]. The developing world has growing investments in science, technology, and innovation in many areas [4–6], including computational biology [7]. These investments have produced positive results in scientific quality in developing countries [8]. Although this is remarkably positive, the emergence of high-level research groups creates a highly competitive environment. We suggest a roadmap of ten simple rules for writing a consistent and convincing research project, which may be useful for researchers in Brazil and other emerging economies. There are several funding agencies in Brazil, and two of them—the National Council for Research Development (CNPq) and the Sao Paulo Research Foundation (FAPESP)—are used as examples of how proposals can be better adjusted in order to be successful. The latter represents the state funding agencies. Our ten rules will consider these agencies as the generic targets of proposals. When describing the ten rules below, we consider applications for research grant proposals and for MSc and PhD fellowships.

Phenolic Compounds in Plants: Implications for Bioenergy

Lignin is a copolymer of three main hydroxycinnamyl alcohols identified as p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units. The highly condensed matrix (core lignin) may also be associated with low-molecular phenolics as hydroxycinnamic acids mainly p-coumaric, caffeic, ferulic, and sinapic acids dubbed noncore lignins. Lignin confers hydrophobicity and mechanical and chemical strength for tissues, providing a barrier against the attack of pathogens and herbivores. The content and composition of lignin are strongly affected by biotic and abiotic stresses. Besides core and noncore lignin, free phenolic compounds perform a relevant activity in response to plant stresses. The toxicity of allelochemicals is partially due to their ability to bind and inhibit enzyme activities. The presence of lignin imposes a physical barrier to the action of enzymes in saccharification of plant cell wall polysaccharides to the production of cellulosic ethanol. The presence of endogenous phenolic compounds as well as treatments to degrade lignin, in turn, release phenolic compounds that adsorb and inhibit cellulases, xylanases, and accessory enzymes. This chapter provides basic information on phenolic compounds of interest to support the sustainable use of alga and plant biomasses as raw materials for the production of biofuels discussing the main approaches ongoing to reduce their negative impact in biomass saccharification.