Neutrophils represent the first line of host cellular defense against various pathogens. The most recently described microbicidal mechanism of these cells is the release of neutrophil extracellular traps (NET). Currently, a wide range of chemical and biological stimuli are known to induce this response; however, the effect of short-chain fatty acids (SCFAs) on the induction of NET is still unknown. SCFAs are produced mainly by bacterial fermentation of dietary fiber and are found in host tissues and blood. This study aimed to determine whether physiological levels of SCFAs can induce the formation of NET. Previously reported concentrations of SCFAs (as found in the colonic lumen and peripheral blood in postprandial and basal states) were used to stimulate the neutrophils. In order to determine the signaling pathway utilized by SCFAs, we tested the inhibition of the Free Fatty Acid 2 Receptor (FFA2R) expressed in neutrophils using CATPB, the inhibitor of FFA2R, genistein, an inhibitor of the downstream Gα/q11 proteins and DPI, an inhibitor of the NADPH oxidase complex. The SCFAs at colonic intestinal lumen concentrations were able to induce the formation of NET, and when tested at concentrations found in the peripheral blood, only acetic acid at 100 μM (fasting equivalent) and 700 μM (postprandial equivalent) was found to induce the formation of NET. The administration of the competitive inhibitor against the receptor or blockade of relevant G protein signaling and the inhibition of NADPH oxidase complex decreased NET release. SCFAs stimulate NET formation in vitro and this effect is mediated, in part, by the FFA2R.

Derepressed mutant PR-22 was obtained by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) mutagenic treatment of Cellulomonas flavigena PN-120. This mutant improved its xylanolytic activity from 26.9 to 40 U mg(-1) and cellulolytic activity from 1.9 to 4 U mg(-1); this represented rates almost 2 and 1.5 times higher, respectively, compared to its parent strain growing in sugarcane bagasse. Either glucose or cellobiose was added to cultures of C. flavigena PN-120 and mutant PR-22 induced with sugarcane bagasse in batch culture. The inhibitory effect of glucose on xylanase activity was more noticeable for parent strain PN-120 than for mutant PR-22. When 20 mM glucose was added, the xylanolytic activity decreased 41% compared to the culture grown without glucose in mutant PR-22, whereas in the PN-120 strain the xylanolytic activity decreased by 49% at the same conditions compared to its own control. Addition of 10 and 15 mM of glucose did not adversely affect CMCase activity in PR-22, but glucose at 20 mM inhibited the enzymatic activity by 28%. The CMCase activity of the PN-120 strain was more sensitive to glucose than PR-22, with a reduction of CMCase activity in the range of 20-32%. Cellobiose had a more significant effect on xylanase and CMCase activities than glucose did in the mutant PR-22 and parent strain. Nevertheless, the activities under both conditions were always higher in the mutant PR-22 than in the PN-120 strain. Enzymatic saccharification experiments showed that it is possible to accumulate up to 10 g l(-1) of total soluble sugars from pretreated sugarcane bagasse with the concentrated enzymatic crude extract from mutant PR-22.

Biochemical and metabolic interpretation of microbial growth is an important topic in bioreactor design. We intend to address valuable information about the relation of critical operation variables and the simulation of bioprocesses with unstructured and structured kinetic models. Process parameters such as nutrient supply, pH, dissolved oxygen, and metabolic end-products directly impact the physiology and metabolism of microorganisms. Changes in the membrane as well as cell viability are of interest since protein expression and maturation in prokaryota are directly related to membrane integrity. This chapter intends to deliver an insight of different alternatives in kinetic modeling.

This work studies the sequential execution of dilute sulfuric acid (DAP) (0.1-0.75 %, v/v) and dilute sodium hydroxide (AKP) (0.25-3 %, w/v) [i.e., DAP followed by AKP (DAP+AKP) and vice versa (AKP+DAP)] at low temperatures (<121 °C) and short reaction times (5-60 min) for maximizing sugar recovery in the enzymatic hydrolysis of wheat straw with low enzyme dosage. The pretreatment effectiveness was measured by the sum of the severity factors of both pretreatments and the saccharification yield achieved in the subsequent stage of enzymatic hydrolysis. Degradation compounds were quantified and mass balance calculations were carried out for each pretreatment sequence to verify the correct account of the input biomass and output products. Results show that sequential pretreatments (AKP+DAP and DAP+AKP) had a positive effect in enzyme accessibility thus improving monosaccharide yields compared to single DAP and AKP pretreatments. DAP+AKP achieved a high xylose yield (ca. 0.867 of theoretical) at the DAP stage, while no xylose monosaccharides were detected in the subsequent AKP. After enzyme saccharification of double-pretreated solids, the total monosaccharide yield was 0.786 (of theoretical). For AKP+DAP sequence, lower results were obtained (total monosaccharide yield 0.783 of theoretical). Sequential pretreatments total yields increased by 21 % compared to single pretreatments. AKP removed more than half of the lignin from the wheat straw in all cases. Acid and alkali concentrations played a relevant role in all pretreatment sequences, while reaction time and temperature were less important with an almost-linear effect on the total monosaccharide yields.