BackgroundDelignification pretreatments of biomass and methods to assess their efficacy are crucial for biomass-to-biofuels research and technology. Here, we applied confocal and fluorescence lifetime imaging microscopy (FLIM) using one- and two-photon excitation to map the lignin distribution within bagasse fibers pretreated with acid and alkali. The evaluated spectra and decay times are correlated with previously calculated lignin fractions. We have also investigated the influence of the pretreatment on the lignin distribution in the cell wall by analyzing the changes in the fluorescence characteristics using two-photon excitation. Eucalyptus fibers were also analyzed for comparison.ResultsFluorescence spectra and variations of the decay time correlate well with the delignification yield and the lignin distribution. The decay dependences are considered two-exponential, one with a rapid (τ1) and the other with a slow (τ2) decay time. The fastest decay is associated to concentrated lignin in the bagasse and has a low sensitivity to the treatment. The fluorescence decay time became longer with the increase of the alkali concentration used in the treatment, which corresponds to lignin emission in a less concentrated environment. In addition, the two-photon fluorescence spectrum is very sensitive to lignin content and accumulation in the cell wall, broadening with the acid pretreatment and narrowing with the alkali one. Heterogeneity of the pretreated cell wall was observed.ConclusionsOur results reveal lignin domains with different concentration levels. The acid pretreatment caused a disorder in the arrangement of lignin and its accumulation in the external border of the cell wall. The alkali pretreatment efficiently removed lignin from the middle of the bagasse fibers, but was less effective in its removal from their surfaces. Our results evidenced a strong correlation between the decay times of the lignin fluorescence and its distribution within the cell wall. A new variety of lignin fluorescence states were accessed by two-photon excitation, which allowed an even broader, but complementary, optical characterization of lignocellulosic materials. These results suggest that the lignin arrangement in untreated bagasse fiber is based on a well-organized nanoenvironment that favors a very low level of interaction between the molecules.

In this work, we evaluated the potential application of fluorescence spectroscopy, associated with the canonical polyadic/parallel factor analysis and principal component analysis, to monitor the dissolved organic matter (DOM) generated from a slaughterhouse industry. During the monitoring process, we analyzed the residual water at the entrance and exit sites of the slaughterhouse effluent treatment as well as downstream and upstream the effluent receiving water body of a local river. The results revealed that the fluorescence analysis was able to identify proteins, chlorophylls, and humic substances at the entrance and exit sites of the slaughterhouse treatment plant and humic substances at the river water bodies. Our data also demonstrated that the industrial effluent discharged into the river did not impact the receiving water body quality as determined by the biological and humification indices obtained by fluorescence analysis, which was confirmed by conventional physicochemical analysis. In summary, the present findings indicate that fluorescence spectroscopy, in association with multivariate analysis, can be successfully applied as an analytical tool for evaluating the quality of DOM in slaughterhouse wastewater.

Dedico esse trabalho especialmente a minha família, primeiramente ao meu avô Adélio da Conceição (em memória), te amo muito; a minha querida avó Amélia, a minha queria madrinha e mãe Marlene e ao meu amado pai Alcione. Em especial a minha querida e amada namorada Aline. AGRADECIMENTOS *Ao meu querido e eterno avô Adélio da Conceição (em memória) e minha querida avó Amélia por sempre acreditar em mim, amo muito vocês! *A minha querida madrinha, mãe e amiga Marlene Pereira da Conceição por estar sempre comigo durante toda a minha vida, nos momentos difíceis e bons, te amo muito dinda! *Ao meu pai Alcione da Conceição. Pai o senhor é tudo para mim! *A minha amada namorada, mulher da minha vida, Aline Marques Leite por ter me acompanhado durante toda a minha formação, desde a graduação e por ter me aguentado por todo esse tempo em que estamos juntos, te amo muito vida! *Ao Professor Dr. Francisco Eduardo Gontijo Guimarães, que nos anos de convivência, muito me ensinou, contribuindo para meu crescimento científico, intelectual e pessoal! *Ao meu tio Adilson Pereira da Conceição! *Aos amigos Luzia Targino Valente e Joaquim Bernadino Valente! *Ao grande amigo Gabriel Perlin Sari pelas nossas ótimas horas de conversa! *Aos amigos que me receberam aqui em