•Efficiency of anaerobic digestion is hampered due to microalgae cell wall.•Organic matter solubilisation and improved biodegradability was achieved by all thermal pretreatments.•Thermal ...pretreatments enhanced hydrolysis rate constant and thus faster biogas production.•Carbohydrates solubilised provided a fairly close estimation for methane production.•Best case scenario was achieved by subjecting biomass to 160°C which resulted in 64% methane yield enhancement.
This study investigates the effect of high pressure thermal hydrolysis on organic matter solubilisation and biogas production from Chlorella vulgaris biomass. Microalgae biomass was subjected to three temperatures, namely 140, 160, and 180°C and two heating times (10 and 20min). Results showed that carbohydrates release prevailed over proteins. Carbohydrates were solubilised concomitantly with increasing temperatures. According to the infrared spectra and monomeric sugars determined in the pretreated medium, temperatures applied clearly affected the solubilisation of structural carbohydrates of the microalgae cell wall. Likewise, thermal pretreatment provided enhanced methane production with regard to the raw algal biomass. Enhanced hydrolysis rate constant supported faster biogas production. Regardless the heating time employed, increasing temperatures depicted increasing methane production. Even thought, organic matter solubilisation was greater at 180°C, the anaerobic biodegradability did not show the same trend. This fact was ascribed to the formation of reaction products that hampered methane production. Best case scenario was achieved by subjecting biomass to 160°C which resulted in 64% methane yield enhancement.
Generation of mRNA isoforms by alternative polyadenylation (APA) and their involvement in regulation of fungal cellular processes, including virulence, remains elusive. Here, we investigated ...genome-wide polyadenylation site (PAS) selection in the rice blast fungus to understand how APA regulates pathogenicity.
More than half of Magnaporthe oryzae transcripts undergo APA and show novel motifs in their PAS region. Transcripts with shorter 30UTRs are more stable and abundant in polysomal fractions, suggesting they are being translated more efficiently. Importantly, rice colonization increases the use of distal PASs of pathogenicity genes, especially those participating in signalling pathways like 14-3-3B, whose long 30UTR is required for infection.
Cleavage factor I (CFI) Rbp35 regulates expression and distal PAS selection of virulence and signalling-associated genes, tRNAs and transposable elements, pointing its potential to drive genomic rearrangements and pathogen evolution. We propose a noncanonical PAS selection mechanism for Rbp35 that recognizes UGUAH, unlike humans, without CFI25.
Our results showed that APA controls turnover and translation of transcripts involved in fungal growth and environmental adaptation. Furthermore, these data provide useful information for enhancing genome annotations and for cross-species comparisons of PASs and PAS usage within the fungal kingdom and the tree of life.
Cell disruption is one of the most critical steps affecting the economy and yields of biotechnological processes for producing biofuels from microalgae. Enzymatic cell disruption has shown ...competitive results compared to mechanical or chemical methods. However, the addition of enzymes implies an associated cost in the overall production process. Recent studies have employed algicidal microorganisms to perform enzymatic cell disruption and degradation of microalgae biomass in order to reduce this associated cost. Algicidal microorganisms induce microalgae growth inhibition, death and subsequent lysis. Secreted algicidal molecules and enzymes produced by bacteria, cyanobacteria, viruses and the microalga themselves that are capable of inducing algal death are classified, and the known modes of action are described along with insights into cell-to-cell interaction and communication.
This review aims to provide information regarding microalgae degradation by microorganisms and secreted algicidal substances that would be useful for microalgae cell breakdown in biofuels production processes. A better understanding of algae-to-algae communication and the specific mechanisms of algal cell lysis is expected to be an important breakthrough for the broader application of algicidal microorganisms in biological cell disruption and the production of biofuels from microalgae biomass.
•Algicidal microorganisms induce microalgae growth inhibition, death and subsequent lysis.•Degradation of microalgae is an enzymatic disruption method.•Microalgal disruption by microorganisms is strain and cell wall-specific.•Algicidal substances are classified and their modes of action are described.
The establishment of polarity is a critical process in pathogenic fungi, mediating infection-related morphogenesis and host tissue invasion. Here, we report the identification of TPC1 (Transcription ...factor for Polarity Control 1), which regulates invasive polarized growth in the rice blast fungus Magnaporthe oryzae. TPC1 encodes a putative transcription factor of the fungal Zn(II)2Cys6 family, exclusive to filamentous fungi. Tpc1-deficient mutants show severe defects in conidiogenesis, infection-associated autophagy, glycogen and lipid metabolism, and plant tissue colonisation. By tracking actin-binding proteins, septin-5 and autophagosome components, we show that Tpc1 regulates cytoskeletal dynamics and infection-associated autophagy during appressorium-mediated plant penetration. We found that Tpc1 interacts with Mst12 and modulates its DNA-binding activity, while Tpc1 nuclear localisation also depends on the MAP kinase Pmk1, consistent with the involvement of Tpc1 in this signalling pathway, which is critical for appressorium development. Importantly, Tpc1 directly regulates NOXD expression, the p22phox subunit of the fungal NADPH oxidase complex via an interaction with Mst12. Tpc1 therefore controls spatial and temporal regulation of cortical F-actin through regulation of the NADPH oxidase complex during appressorium re-polarisation. Consequently, Tpc1 is a core developmental regulator in filamentous fungi, linking the regulated synthesis of reactive oxygen species and the Pmk1 pathway, with polarity control during host invasion.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Laccase detoxification removes phenolic compounds in steam-pretreated materials.•Laccase action diminishes glucose release during the enzymatic hydrolysis.•Lignin oxidation by laccase induces an ...inhibitory effect on enzymatic hydrolysis.•Lignin and phenols are key players in the inhibition of cellulases by laccase.•The amount of free and active cellulases is critical when laccases are applied.
Phenols are known as inhibitors for cellulases and fermentative microorganisms in bioethanol production processes. The addition of laccases removes the phenolic compounds and subsequently reduces the lag phase of the fermentative microorganism. However, the application of laccases diminishes glucose release during the enzymatic hydrolysis. In this study a model cellulosic substrate (Sigmacell) together with lignin extract, whole steam-pretreated wheat straw (slurry) and its water insoluble solid fraction (WIS) were subjected to enzymatic hydrolysis to evaluate the effects of laccase treatment in presence of lignin and phenols. The presence of laccase in enzymatic hydrolysis of Sigmacell with lignin extract reduced glucose yield by 37% compared with assays without laccase. Furthermore, this reduction was even more marked in presence of phenols (55% reduction). Interestingly, when hydrolyzing WIS, the addition of phenols coupled with laccase treatment did not show a reduction when compared with only laccase addition. This fact suggests the key role of lignin in the hydrolysis inhibition since in WIS the ratio cellulase per gram of lignin was much lower than in Sigmacell experiments. Finally, the lower cellobiose and xylose recoveries point out that phenolic oligomers formed by laccase oxidation play important roles in the inhibition of endoglucanases, cellobiohydrolases and xylanases. To conclude, the proportion of lignin and the composition of phenols are key players in the inhibition of cellulases when the enzymatic hydrolysis is combined with laccases detoxification.
Summary
Generation of
mRNA
isoforms by alternative polyadenylation (
APA
) and their involvement in regulation of fungal cellular processes, including virulence, remains elusive. Here, we ...investigated genome‐wide polyadenylation site (
PAS
) selection in the rice blast fungus to understand how
APA
regulates pathogenicity.
More than half of
Magnaporthe oryzae
transcripts undergo
APA
and show novel motifs in their
PAS
region. Transcripts with shorter 3′
UTR
s are more stable and abundant in polysomal fractions, suggesting they are being translated more efficiently. Importantly, rice colonization increases the use of distal
PAS
s of pathogenicity genes, especially those participating in signalling pathways like
14‐3‐3B
, whose long 3′
UTR
is required for infection.
Cleavage factor I (
CFI
) Rbp35 regulates expression and distal
PAS
selection of virulence and signalling‐associated genes,
tRNA
s and transposable elements, pointing its potential to drive genomic rearrangements and pathogen evolution. We propose a noncanonical
PAS
selection mechanism for Rbp35 that recognizes
UGUAH
, unlike humans, without
CFI
25.
Our results showed that
APA
controls turnover and translation of transcripts involved in fungal growth and environmental adaptation. Furthermore, these data provide useful information for enhancing genome annotations and for cross‐species comparisons of
PAS
s and
PAS
usage within the fungal kingdom and the tree of life.
Laccase enzymes are promising detoxifying agents during lignocellulosic bioethanol production from wheat straw. However, they affect the enzymatic hydrolysis of this material by lowering the glucose ...recovery yields. This work aimed at explaining the negative effects of laccase on enzymatic hydrolysis. Relative glucose recovery in presence of laccase (10IU/g substrate) with model cellulosic substrate (Sigmacell) at 10% (w/v) was almost 10% points lower (P<0.01) than in the absence of laccase. This fact could be due to an increase in the competition of cellulose binding sites between the enzymes and a slight inhibition of β-glucosidase activity. However, enzymatic hydrolysis and infrared spectra of laccase-treated and untreated wheat straw filtered pretreated residue (WS-FPR), revealed that a grafting process of phenoxy radicals onto the lignin fiber could be the cause of diminished accessibility of cellulases to cellulose in pretreated wheat straw.
In Clostridium acetobutylicum, FeFe-hydrogenase is involved in hydrogen production in vivo by transferring electrons from physiological electron donors, ferredoxin and flavodoxin, to protons. In this ...report, by modifications of the purification procedure, the specific activity of the enzyme has been improved and its complete catalytic profile in hydrogen evolution, hydrogen uptake, proton/deuterium exchange and para-H₂/ortho-H₂ conversion has been determined. The major ferredoxin expressed in the solvent-producing C. acetobutylicum cells was purified and identified as encoded by ORF CAC0303. Clostridium acetobutylicum recombinant holoflavodoxin CAC0587 was also purified. The kinetic parameters of C. acetobutylicum FeFe-hydrogenase for both physiological partners, ferredoxin CAC0303 and flavodoxin CAC0587, are reported for hydrogen uptake and hydrogen evolution activities.
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