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.
Conventional cytogenetics are the gold standard for the identification of chromosomal alterations recurrent in myeloid neoplasms. Some next-generation sequencing (NGS) panels are designed for the ...detection of copy number variations (CNV) or translocations; however, their use is far from being widespread. Here we report on the results of a commercial panel including frequent mutations, CNVs and translocations in myeloid neoplasms. Frequent chromosomal alterations were analyzed by NGS in 135 patients with myeloid neoplasms and three with acute lymphoblastic leukemia. NGS analysis was performed using the enrichment-capture Myeloid Neoplasm-GeneSGKit (Sistemas Genómicos, Spain) gene panel including 35 genes for mutational analysis and frequent CNVs and translocations. NGS results were validated with cytogenetics and/or MLPA when possible. A total of 66 frequent alterations included in NGS panel were detected, 48 of them detected by NGS and cytogenetics. Ten of them were observed only by cytogenetics (mainly trisomy 8), and another eight only by NGS (mainly deletion of 12p). Aside from this, 38 secondary CNVs were detected in any of the genes included mainly for mutational analysis. NGS represents a reliable complementary source of information for the analysis of CNVs and translocations. Moreover, NGS could be a useful tool for the detection of alterations not observed by conventional cytogenetics.
•Cultivation in urban wastewater mediated carbohydrate accumulation in C. vulgaris.•C. vulgaris floc formation did not affect enzymatic hydrolysis efficiency.•Despite of the macromolecular profile, ...protease pretreatment of C. vulgaris evidenced high hydrolysis efficiency.•Pretreated carbohydrate-rich C. vulgaris provided higher methane yield than protein-rich biomass.
Two biocatalysts, namely carbohydrases and proteases, were assessed for organic matter solubilisation and methane yield enhancement of microalgae biomass. This study evidenced Chlorella vulgaris carbohydrate accumulation (40% on VSS basis) when grown in urban wastewater. Despite of the carbohydrate prevailing fraction, protease pretreatment showed higher organic matter hydrolysis efficiency (54%). Microscopic observation revealed that carbohydrases affected slightly the cell wall while protease was not selective to wall constituents. Raw and pretreated biomass was digested at 1.5kgtCODm−3day−1 organic loading rate (OLR1) and 20days hydraulic retention time (HRT). The highest methane yield (137mLCH4gCODin−1) was achieved in the reactor fed with protease pretreated C. vulgaris. Additionally, anaerobic digestion was conducted at OLR2 (3kgtCODm−3day−1) and HRT (15days). When compared to raw biomass, methane yield increased 5- and 6.3-fold at OLR1 and OLR2, respectively. No inhibitors were detected during the anaerobic digestion.
Microalgae grown in swine wastewater were used as a promising strategy to produce renewable energy by coupling wastewater bioremediation and biomass revalorization. The efficiency of a microalgae ...consortium treating swine slurry at different temperature (15 and 23 °C) and illumination periods (11 and 14 h) was assessed for biomass growth and nutrient removal at two NH4+ initial concentrations (80 and 250 mg L−1 NH4+). Favourable culture conditions (23 °C and 14 h of illumination) and high ammonium loads resulted in higher biomass production and greater nutrients removal rates. The initial N–NH4+ load determined the removal mechanism, thus ammonia stripping and nitrogen uptake accounted similarly in the case of high NH4+ load, while nitrogen uptake prevailed at low NH4+ load. Under favourable conditions, nitrogen availability in the media determined the composition of the biomass. In this context, carbohydrate-rich biomass was obtained in batch mode while semi-continuous operation resulted in protein-rich biomass. The revalorization of the resultant biomass was evaluated for biogas production. Methane yields in the range of 106–146 and 171 ml CH4 g COD−1 were obtained for the biomasses grown in batch and semi-continuous mode, respectively. Biomass grown under favourable conditions resulted in higher methane yields and closer to the theoretically achievable.
•Microalgae consortium was used for piggery wastewater bioremediation.•Ammonium loads ruled the nitrogen removal mechanism.•Nutrition mode affected nitrogen removal mechanisms and methane yield.•Available media nitrogen determined biomass macromolecular profile.•Biomass grown under favourable conditions exhibited higher methane production.
Development of biofuels such as lignocellulosic
ethanol represents a sustainable alternative in the transport
sector. Wheat straw is a promising feedstock for bioethanol
production in Europe due to ...its large production and high
carbohydrates content. In a process to produce cellulosic
ethanol, previous to the enzymatic hydrolysis to obtain
fermentable sugars and the subsequent fermentation,
a pretreatment step to break down the recalcitrance of
lignocellulose fiber is essential. In this work, a range of
steam explosion pretreatment conditions were evaluated
according to different parameters: sugars recovery,
degradation products generation, and enzymatic hydrolysis
yields. Moreover, the enzymatic hydrolysis process was
also studied at high substrate loadings, since operating at
high solids loading is crucial for large scale development
of ethanol production. Pretreatment at 200°C - 10 min
resulted in higher enzymatic hydrolysis yield (91.7%) and
overall glucose yields (35.4 g glucose/100 g wheat straw)
but also higher production of toxic compound. In turn,
the characteristics of the pretreated wheat straw at lower
severity (Log R0=3.65) correspond to 190°C and 10 min, with
minimal sugars degradation and toxics formation indicated
a great potential for maximizing total sugars production by
using optimal enzyme combinations including accessory
enzymes in the enzymatic hydrolysis step.
•Microalgae anaerobic biodegradability was higher than that of secondary sludge.•Thermal pretreatment was more effective on microalgae than on secondary sludge.•Pretreated microalgae and primary ...sludge codigestion enhanced methane yields by 15%.•Algae and municipal wastewater sludge can be cosubstrates for biogas production.
This study evaluated the feasibility of using microalgae biomass as feedstock for anaerobic digestion together with other biomasses (primary and secondary sludge) normally generated in WWTP. Raw microalgae biomass anaerobic biodegradability (33%) was higher than that of secondary sludge (23%). Thermal pretreatment enhanced 62% and 16% methane yield for Chlorellavulgaris and secondary sludge, respectively. When both substrates were codigested, methane yields remained low. On the other hand, primary sludge supported the highest anaerobic biodegradability (97%) and when combined with thermally pretreated C. vulgaris, methane yields were higher (13–17%) than the ones expected theoretically. Despite the high protein content of those substrates and the high nitrogen mineralization, no ammonia inhibition was detected. Thereby, this study showed that algae biomass is a potential cosubstrate for biogas production together with municipal wastewater sludge.
Microalgae biomass is regarded as a potential feedstock for bioenergy purposes through anaerobic digestion (AD). Even though AD is a well-proven technology, the use of new feedstocks requires ...in-depth studies. A lot of research has been conducted assessing methane yield without paying attention to the anaerobic microbiome and their activities. For such a goal, the present investigation was designed to link methane yield to those two later sludge characteristics. In this sense, different anaerobic sources were tested, namely adapted to microalgae biomass and adapted to sewage sludge.
Despite the registered differences for the anaerobic microbiome analysis and specific methane activities towards model substrates, sludge adapted to digest sewage sludge did not affect the methane yield of
and
sp. Opposite to that, sludge samples adapted to digest microalgae exhibited a concomitant increase in methane yield together with increasing digestion temperatures. More specifically, the values attained were 63.4 ± 1.5, 79.2 ± 3.1 and 108.2 ± 1.9 mL CH
g COD in
for psychrophilic, mesophilic and thermophilic digestions, respectively. While psycro- and mesophilic digestion supported similar yields (most probably linked to their anaerobic microbiome resemblance), the values attained for thermophilic digestion evidenced the usefulness of having a highly specific microbiome. The relative abundance of Firmicutes, particularly
, and Proteobacteria together with an important abundance of hydrogenotrophic methanogens was highlighted in this inoculum.
Overall, this study showed that working with tailored anaerobic microbiome could help avoiding pretreatments devoted to methane yield enhancement.
•Methane production of microalgae biomass is hampered by their cell wall.•Pretreatment should be designed in accordance to the microalgae specie.•Fresh Chlamydomonas reinhardtii exhibited high ...anaerobic biodegradability.•Chlorella vulgaris anaerobic biodegradability was enhanced by 50% using protease pretreatment.
The effect of enzymatic hydrolysis on microalgae organic matter solubilisation and methane production was investigated in this study. Even though both biomasses, Chlamydomonas reinhardtii and Chlorella vulgaris, exhibited similar macromolecular distribution, their cell wall composition provided different behaviors. The addition of carbohydrolase (Viscozyme) and protease (Alcalase) resulted in high carbohydrates and protein solubilisation on both biomasses (86–96%). Despite the high carbohydrate solubilisation with the carbohydrolase, methane production was enhanced by 14% for C. vulgaris, while hydrolyzed C. reinhardtii did not show any improvement. The addition of protease to C. reinhardtii increased methane production by 1.17-fold. The low enhancement achieved together with the inherent high biodegradability of this biomass would not justify the cost associated to the enzyme addition. On the other hand, C. vulgaris hydrolyzed with the protease resulted in 86% anaerobic biodegradability compared to 54% of the raw biomass. Therefore, the application of protease prior anaerobic digestion of C. vulgaris could be a promising approach to decrease the energetic input required for cell wall disruption.
Combined soda and enzyme-catalyzed extrusion pretreatment (bioextrusion) of barley straw was evaluated for bioethanol production. The effect of the enzyme dose on the bioextrudate was for the first ...time analyzed. The enzyme load (5–10 FPU/g DM) had a significant impact on the solubilization of sugars during bioextrusion and also affected the saccharification yield at long incubation times. The solids concentration (17–25% w/w) in the extended incubation of bioextrudates was also studied and its effect on the carbohydrate conversion and sugar release was evaluated. An enzyme dose of 10 FPU/g dry matter and a solids content of 20% (w/w) were selected as the best conditions to submit the bioextrudate to a liquefaction plus simultaneous saccharification and co-fermentation (LSSCF) process using a modified S. cerevisiae strain. At the end of the process, an ethanol concentration close to 38 g/l was obtained, corresponding to a production of 15.8 g ethanol/100 g raw barley straw.
•Combined alkali- and enzyme-extrusion is a suitable pretreatment for barley straw.•The effect of enzyme dose and solids content in sugar release was studied.•Fermentation was carried out with a co-fermenting S. cerevisiae strain.•High glucan and xylan conversions of 75% and 61% respectively were obtained.•Ethanol production reaches 15.8 g per 100 g of raw barley straw.
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