A novel rapid ultrasonication-microwave treatment for total lipid extraction from wet oleaginous yeast biomass for sustainable biodiesel production

Oleaginous yeasts have emerged as a sustainable source of renewable oils for liquid biofuels. However, biodiesel production from them has a few constraints with respect to their cell disruption and lipid extraction techniques. The lipid extraction from oleaginous yeasts commonly includes dewatering and drying of cell biomass, which requires energy and time. The aim of this work was to establish a process for the lipid extraction from wet biomass applying acid catalyzed hot water, as well as microwave, and rapid ultrasonication-microwave treatment together with the conventional Bligh and Dyer method. In the wake of testing all procedures, it was revealed that rapid ultrasonication-microwave treatment has great potential to give high lipid content (70.86% w/w) on the cell dry weight basis. The lipid profile after treatment showed the presence of appropriate quantities of saturated (10.39 ± 0.15%), monounsaturated (76.55 ± 0.19%) and polyunsaturated fatty acids (11.49 ± 0.23%) which further improves biodiesel quality compared to the other methods. To the best of our knowledge, this is the first report of using rapid ultrasonication-microwave treatment for the lipid extraction from wet oleaginous yeast biomass in the literature.

Twenty-first-century chemical odyssey: fuels versus commodities and cell factories versus chemical plants

The harmful effects of pollution from the massive and widespread use of fossil fuels have led various organizations and governments to search for alternative energy sources. To address this, a new energy bioprocess is being developed that utilizes non-edible lignocellulose - the only sustainable source of organic carbon in nature. In this mini-review, we consider the potential use of synthetic biology to develop new-to-nature pathways for the biosynthesis of chemicals that are currently synthesized using classical industrial approaches. The number of industrial processes based on starch or lignocellulose is still very modest. Advances in the area require the development of more efficient approaches to deconstruct plant materials, better exploitation of the catalytic potential of prokaryotes and lower eukaryotes and the identification of new and useful genes for product synthesis. Further research and progress is urgently needed in order for government and industry to achieve the major milestone of transitioning 30% of the total industry to renewable sources by 2050.

Energy balance for biodiesel production processes using microbial oil and scum

Biodiesel production using microbial oil is a promising technology. The main aim of this study is to check practical feasibility (in terms of energy balance) of different biodiesel production processes. Mass and energy balance of biodiesel production have been performed for 3 separate processes: (1) microbial lipid production from T. oleaginosus using waste substrates followed by INRS downstream process (2) microbial lipid production from pure substrate using R. toruloides followed by traditional and INRS downstream process and 3) oil extraction from scum and conversion to biodiesel. It was found that employing waste substrates like crude glycerol and municipal sludge in fermentation reduced the energy input by 50%. While employing biodegradable surfactants and petroleum-diesel as solvent (PD) for lipid extraction and recovery significantly reduced the energy input at cell wall disruption step. Biodiesel production from scum is a two-step process which is fast and energetically favorable.

Producing Oleaginous Microorganisms Using Wastewater: Methods and Guidelines for Lab- and Industrial-Scale Production

Cultivation of oleaginous microorganisms on wastewater provides alternative biofuel options while also acting as a remediation technique for alternative wastewater treatment. This chapter describes guidelines and methods for the production of oleaginous microorganisms-with a focus on microalgae-using wastewater as a growth medium while considering a variety of general challenges for both lab- and industrial-scale production. Cultivation techniques described here range in scale from microplates with 10-mL working volumes, up to multigallon, industrial-scale microorganism cultivation, with a focus on microalgae. This chapter includes guidelines for the preparation of wastewater and selection of oleaginous microorganisms combined with methods for the production of oleaginous microorganisms cultivated using wastewater.

Targeted knockout of phospholipase A2 to increase lipid productivity in Chlamydomonas reinhardtii for biodiesel production

Biofuel derived from microalgae have several advantages over other oleaginous crops, however, still needs to be improved with its cost aspect and can be achieved by developing of a strain with improved lipid productivity. In this study, the CRISPR-Cas9 system was incorporated to carry out a target-specific knockout of the phospholipase A₂ gene in Chlamydomonas reinhardtii. The targeted gene encodes a key enzyme in the Lands cycle. As a result, the mutants showed a characteristic of increased diacylglycerol pool, followed by a higher accumulation of triacylglycerol without being significantly compensated with the cell growth. As a result, the overall lipid productivities of phospholipase A₂ knockout mutants have increased by up to 64.25% (to 80.92 g L^-1 d^-1). This study can provide crucial information for the biodiesel industry.

Performance of a novel photobioreactor for nutrient removal from piggery biogas slurry: Operation parameters, microbial diversity and nutrient recovery potential

Photobioreactor is deemed to be one of limiting factors for the commercial application of wastewater treatment based on microalgae cultivation. In this study, a novel Flat-Plate Continuous Open Photobioreactor (FPCO-PBR) was developed to treat piggery biogas slurry. The operation parameters, microbial stability and nutrient recovery potential of FPCO-PBR were investigated. Results showed that the appropriate influent mode for FPCO-PBR was multi-point or spraying mode. The optimal hydraulic retention time and interval time for biomass harvesting of FPCO-PBR were both 2 d. Nitrogen and phosphorus recovery rate were 30 mg L^-1 d^-1 and 7 mg L^-1 d^-1 respectively under optimal operating parameters. Microbial diversity remained relatively stable in FPCO-PBR. Biomass production rate of FPCO-PBR was 0.47 g L^-1 d^-1 under optimal operating parameters. The revenue generated from biomass was estimated to be 15.06 $ kg^-1, which means that treating one ton of wastewater can generate $ 7.08 in revenue.

Concomitant production of chitosan and lipids from a newly isolated Mucor circinelloides ZSKP for biodiesel production

A newly-isolated oleaginous fungus Mucor circinelloides ZSKP concurrently yielded 21.4% lipids and 11.2% chitosan per gram of biomass. Parameters affecting the co-production were identified using Plackett-Burman design and were statistically optimized using Response Surface Methodology, which resulted in a 3-fold improvement in lipid production. The lipid profile showed a high content of unsaturated fatty acids including oleic (37%), linolenic (14%) and linoleic acids (19%), while palmitic acid was the major saturated fatty acid (21%). A comparative study to evaluate the efficacy of enzymatic (lipase) and chemical treatments for biodiesel production from fungal lipids and sunflower oil revealed enhanced production of biodiesel from fungal lipids. Synthesized biodiesel from M. circinelloides ZSKP satisfied standard specifications and had a higher cetane number (56), lower kinematic viscosity (4.6 mm²/s) and lower acid number (0.03) compared to sunflower oil. Results suggest Mucor circinelloides ZSKP is a promising candidate for implementation of the biorefinery concept.

Conversion of Microbial Lipids to Biodiesel and Basic Lab Tests for Analysis of Fuel-Quality Parameters

This chapter describes lab-scale procedures for the direct conversion of microbial lipids to fatty acid methyl esters (FAMEs) for use as biodiesel fuel. Methods for the gas chromatography analysis of FAME profiles and equations to predict several fuel-quality parameters are detailed herein. This chapter also provides a complete list summarizing each of the fuel quality tests (e.g., sample size and equipment) that are required by ASTM International D6751 regulations for pure biodiesel fuel (B100) or blend stock. Recommendations for the decolorization of microbial lipid sources containing pigments are also included. This resource should provide a guide to basic conversion and characterization of microbial-derived biodiesel fuels and a roadmap for more-detailed testing required to assess commercial feasibility.

Life Cycle Analysis of Producing Microbial Lipids and Biodiesel: Comparison with Plant Lipids

Life Cycle Assessment is the "compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product system throughout its life cycle" (ISO 14040). Examples of environmental impacts include climate change, ozone depletion, toxicity, eutrophication, particulate matter, radiation, and more. In this chapter we describe the process of undertaking an LCA for algal products, considering the ISO 14040 and ISO 14044, standards, as well as information from the European Renewable Energy Directive. We describe popular software packages, and the approach of purely using a spreadsheet with an example of algae- and soy-based biodiesel.

Producing Oleaginous Organisms Using Food Waste: Challenges and Outcomes

With organic or food waste being one of the main constituents of the total urban waste generated, it not only makes it essential to seek means for its safe disposal but at the same time reiterates the huge potential that lies with the proper utilization of such a widely available resource. Oleaginous microbes that are effective in producing or storing oil would use food waste rich in carbohydrates, lipids, and proteins, and this oil in turn could be an alternative feedstock for the production of biofuels. However, there are few challenges in the process. The various challenges in this process and methods to address them are discussed in the present chapter.

Potential of aquatic oomycete as a novel feedstock for microbial oil grown on waste sugarcane bagasse

Biodiesel production from vegetable oils is not sustainable and economical due to the food crisis worldwide. The development of a cost-effective non-edible feedstock is essential. In this study, we proposed to use aquatic oomycetes for microbial oils, which are cellulolytic fungus-like filamentous eukaryotic microorganisms, commonly known as water molds. They differ from true fungi as cellulose is present in their cell wall and chitin is absent. They show parasitic as well as saprophytic nature and have great potential to utilize decaying animal and plant debris in freshwater habitats. To study the triacylglycerol (TAG) accumulation in the aquatic oomycetes, the isolated water mold Achlya diffusa was cultivated under semi-solid-state conditions on waste sugarcane bagasse, which was compared with the cultivation in Czapek (DOX) medium. A. diffusa grown on waste sugarcane bagasse showed large lipid droplets in its cellular compartment and synthesized 124.03 ± 1.93 mg/gds cell dry weight with 50.26 ± 1.76% w/w lipid content. The cell dry weight and lipid content of this water mold decreased to 89.54 ± 1.21 mg/gds and 38.82% w/w, respectively, when cultivated on standard medium Czapek-Dox agar (CDA). For the fatty acid profile of A. diffusa grown in sugarcane bagasse and CDA, in situ transesterification (IST) and indirect transesterification (IDT) approaches were evaluated. The lipid profile of this mold revealed the presence of C_12:0, C_14:0, C_16:0, C_18:0, C_18:1, C_18:2, C_20:0, and C_21:0 fatty acids, which is similar to vegetable oils. The biodiesel properties of the lipids obtained from A. diffusa satisfied the limits as determined by international standards ASTM-D6751 and EN-14214 demonstrating its suitability as a fuel for diesel engines.

Responses and successions of sulfonamides, tetracyclines and fluoroquinolones resistance genes and bacterial community during the short-term storage of biogas residue and organic manure under the incubator and natural conditions

Biogas residue and organic manure are frequently used for crop planting. However, the evaluation of antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs) and bacterial community before their applications to fields is still lacking. This study monitored the variations of bacteria resistant to sulfadiazine, tetracycline and norfloxacin, 57 resistance genes for sulfonamides, tetracyclines and fluoroquinolones as well as the bacterial community during the 28-day aerobic storage of biogas residue and organic manure by using viable plate counts, high-throughput qPCR and Illumina MiSeq sequencing methods. Then two storage conditions, incubator (25 °C) and natural environment, were used to assess the responses of ARB and ARGs to the environmental factors. Results showed that a total of 35 and 21 ARGs were detected in biogas residue and organic manure, respectively. ARB and ARGs were enriched up to 8.01-fold in biogas residue after the 28-day storage, but varied in a narrow range during the storage of organic manure. Compared with the incubator condition, the proliferation of ARB and ARGs in biogas residue under the natural condition was relatively inhibited by the varied and complicated environmental factors. However, we found that there was no significant difference of ARB and ARGs in organic manure between the incubator and natural conditions. Bacterial community was also shifted during the storage of biogas residue, especially Bacteroidetes_VC2.1_Bac22, Aequorivita, Luteimonas and Arenimonas. Network analysis revealed that the relationship in biogas residue was much more complicated than that in organic manure, which ultimately resulted in large successions of ARB and ARGs during the short-term storage of biogas residue. Therefore, we suggest that further measures should be taken before the application of biogas residue to fields.

Microbial activity response to hydrogen injection in thermophilic anaerobic digesters revealed by genome-centric metatranscriptomics

BACKGROUND

The expansion of renewable energy produced by windmills and photovoltaic panels has generated a considerable electricity surplus, which can be utilized in water electrolysis systems for hydrogen production. The resulting hydrogen can then be funneled to anaerobic digesters for biogas upgrading (biomethanation) purposes (power-to-methane) or to produce high value-added compounds such as short-chain fatty acids (power-to-chemicals). Genome-centric metagenomics and metatranscriptomic analyses were performed to better understand the metabolic dynamics associated with H₂ injection in two different configurations of anaerobic digesters treating acidic wastes, specifically cheese manufacturing byproducts. These approaches revealed the key-genes involved in methanation and carbon fixation pathways at species level.

RESULTS

The biogas upgrading process in the single-stage configuration increased the CH₄ content by 7%. The dominant methanogenic species responsible for the upregulation of the hydrogenotrophic pathway in this reactor was Methanothermobacter wolfeii UC0008. In the two-stage configuration, H₂ injection induced an upregulation of CO₂ fixation pathways producing short-chain fatty acids, mainly acetate and butyrate. In this configuration, the abundant species Anaerobaculum hydrogeniformans UC0046 and Defluviitoga tunisiensis UC0050 primarily upregulated genes related to electron transport chains, suggesting putative syntrophisms with hydrogen scavenger microbes. Interestingly, Tepidanaerobacter acetatoxydans UC0018 did not act as an acetate-oxidizer in either reactor configurations, and instead regulated pathways involved in acetate production and uptake. A putative syntrophic association between Coprothermobacter proteolyticus UC0011 and M. wolfeii UC0008 was proposed in the two-stage reactor. In order to support the transcriptomic findings regarding the hydrogen utilization routes, an advanced bioconversion model was adapted for the simulation of the single- and two-stage reactor setups.

CONCLUSIONS

This is the first study investigating biogas reactor metatranscriptome dynamics following hydrogen injection for biomethanation and carbon fixation to short-chain fatty acids purposes. The same microbes showed different patterns of metabolic regulation in the two reactor configurations. It was observed an effect of the specialized acidogenic reactor on the overall microbial consortium composition and activity in the two-stage digester. There were also suggested the main species responsible for methanation, short-chain fatty acids production, and electron transport chain mechanisms, in both reactor configurations.

Human gut microbe co-cultures have greater potential than monocultures for food waste remediation to commodity chemicals

Food waste represents an underutilized resource for commodity chemical generation. Constituents of the human gut microbiota that are already adapted to a food waste stream could be repurposed for useful chemical production. Industrial fermentations utilizing these microbes maintain organisms in isolation; however, microbial consortia offer an attractive alternative to monocultures in that metabolic interactions may result in more efficient processes with higher yields. Here we computationally assess the ability of co-cultures vs. monocultures to anaerobically convert a Western diet to commodity chemicals. The combination of genome-scale metabolic models with flux-balance analysis predicts that every organism analyzed can benefit from interactions with another microbe, as evidenced by increased biomass fluxes in co-culture vs. monoculture. Furthermore, microbe combinations result in emergent or increased commodity chemical production including butanol, methane, formaldehyde, propionate, hydrogen gas, and urea. These overproducing co-cultures are enriched for mutualistic and commensal interactions. Using Clostridium beijerinckii co-cultures as representative examples, models predict cross-fed metabolites will simultaneously modify multiple internal pathways, evident by different internal metabolic network structures. Differences in degree and betweenness centrality of hub precursor metabolites were correlated to C. beijerinckii metabolic outputs, and thus demonstrate the potential of co-cultures to differentially direct metabolisms to useful products.

Pseudallescheria boydii and Meyerozyma guilliermondii: behavior of deteriogenic fungi during simulated storage of diesel, biodiesel, and B10 blend in Brazil

Due to their renewable and sustainable nature, biodiesel blends boost studies predicting their stability during storage. Besides chemical degradation, biodiesel is more susceptible to biodegradation due to its raw composition. The aim of this work was to evaluate the deteriogenic potential (growth and degradation) of Pseudallescheria boydii and Meyerozyma guilliermondii in degrading pure diesel (B0), pure biodiesel (B100), and a B10 blend in mineral medium during storage. The biodeterioration susceptibility at different fuel ratios and in BH minimal mineral medium were evaluated. The biomass measurements of P. boydii during 45 days indicated higher biomass production in the B10 blend. The growth curve of M. guilliermondii showed similar growth in B10 and B100. Although there was no significant production of biosurfactant, lipase production was detected in the tributyrin agar medium of both microorganisms. The main compounds identified in the aqueous phase by GC-MS were alcohols, esters, acids, sulfur, ketones, and phenols. The results showed that P. boydii grew at the expense of fuels, degrading biodiesel esters, and diesel hydrocarbons. M. guilliermondii grew in B100 and B10; however, degradation was not detected.

Interfacing nature's catalytic machinery with synthetic materials for semi-artificial photosynthesis

Semi-artificial photosynthetic systems aim to overcome the limitations of natural and artificial photosynthesis while providing an opportunity to investigate their respective functionality. The progress and studies of these hybrid systems is the focus of this forward-looking perspective. In this Review, we discuss how enzymes have been interfaced with synthetic materials and employed for semi-artificial fuel production. In parallel, we examine how more complex living cellular systems can be recruited for in vivo fuel and chemical production in an approach where inorganic nanostructures are hybridized with photosynthetic and non-photosynthetic microorganisms. Side-by-side comparisons reveal strengths and limitations of enzyme- and microorganism-based hybrid systems, and how lessons extracted from studying enzyme hybrids can be applied to investigations of microorganism-hybrid devices. We conclude by putting semi-artificial photosynthesis in the context of its own ambitions and discuss how it can help address the grand challenges facing artificial systems for the efficient generation of solar fuels and chemicals.

Microbial community composition and diversity in rice straw digestion bioreactors with and without dairy manure

Anaerobic digestion (AD) uses a range of substrates to generate biogas, including energy crops such as globally abundant rice straw (RS). Unfortunately, RS is high in lignocellulosic material and has high to C:N ratios (~80:1), which makes it (alone) a comparatively poor substrate for AD. Co-digestion with dairy manure (DM) has been promoted as a method for balancing C:N ratios to improve RS AD whilst also treating another farm waste and co-producing a potentially useful fertiliser. However, past co-digestion studies have not directly compared RS AD microbial communities with and without DM additions, which has made it hard to assess all impacts of DM addition to RS AD processes. Here, four RS:DM ratios were contrasted in identical semi-continuous-fed AD bioreactors, and 100% RS was found to produce the highest specific methane yields (112 mL CH4/g VS/day; VS, volatile solids), which is over double yields achieved in the reactor with the highest DM content (30:70 RS:DM by mass; 48 mL CH4/g VS/day). To underpin these data, microbial communities were sequenced and characterised across the four reactors. Dominant operational taxonomic units (OTUs) in the 100% RS unit were Bacteroidetes/Firmicutes, whereas the 30:70 RS:DM unit was dominated by Proteobacteria/Spirochaetes, suggesting major microbial community shifts occur with DM additions. However, community richness was lowest with 100% RS (despite higher specific yields), suggesting particular OTUs may be more important to yields than microbial diversity. Further, ambient VFA and VS levels were significantly higher when no DM was added, suggesting DM-amended reactors may cope better with higher organic loading rates (OLR). Results show that RS AD without DM addition is feasible, although co-digestion with DM will probably allow higher OLRs, resulting in great RS throughput in farm AD units.

Anaerobic Process

A review of the literatures published in 2017 on topics relating to anaerobic process issues in the improvement of biogas production and fermentation efficiency of various kinds of organic waste. New process methodology and technology of digestion is also presented. This review is divided into the following sections: pretreatment, organic waste and co-digestion, multiple-stage process, process methodology and technology.

Potential of Lentibacillus sp. NS12IITR for production of lipids with enriched branched-chain fatty acids for improving biodiesel properties along with hydrocarbon co-production

Hypersaline environment is inhabited by array of microbes which have the potential to produce industrially important products. This study explored biomass and lipid production potential of the halophilic bacterium, strain NS12IITR which was isolated from Sambhar Lake, Rajasthan. Sequencing and phylogenetic analysis revealed that the bacterium belonged to genus Lentibacillus. The salient feature of the isolate is its ability to accumulate total cellular lipid up to 18.9 ± 0.45% of dry cell weight. In addition, trans-esterification of extracted lipid yielded 77.6 ± 5.56% of total esters as methyl ester of branched-chain fatty acids (BCFAs). To assess the nature of extracted lipid, lipid sample was fractionated on the silicic acid column, which demonstrated that 49.03 ± 1.35% of the total lipids was neutral in nature. Trans-esterification of the neutral lipid fraction yielded 60.62 ± 4.88% of total esters as methyl ester of BCFAs. Methyl esters of BCFAs were present in trans-esterified products of neutral as well as polar lipid fractions. Furthermore, the isolate produced hydrocarbons both extracellularly (C₁₀-C₃₀) and intra-cellularly (C₁₅-C₂₈). The concentration of extracellular hydrocarbon (21.11 ± 0.78 mg/L) synthesized by strain NS12IITR is in close agreement with the yield reported from other hydrocarbon producing bacteria. This is hereby a first report on the co-production of lipids and hydrocarbon from a halophilic bacterium. The production of neutral lipid with high percentage of BCFAs and co-production of hydrocarbons makes the isolate NS12IITR a potential claimant for biofuel production.

Transcription of lignocellulose-decomposition associated genes, enzyme activities and production of ethanol upon bioconversion of waste substrate by Phlebia radiata

Previously identified twelve plant cell wall degradation-associated genes of the white rot fungus Phlebia radiata were studied by RT-qPCR in semi-aerobic solid-state cultures on lignocellulose waste material, and on glucose-containing reference medium. Wood-decay-involved enzyme activities and ethanol production were followed to elucidate both the degradative and fermentative processes. On the waste lignocellulose substrate, P. radiata carbohydrate-active enzyme (CAZy) genes encoding cellulolytic and hemicellulolytic activities were significantly upregulated whereas genes involved in lignin modification displayed a more complex response. Two lignin peroxidase genes were differentially expressed on waste lignocellulose compared to glucose medium, whereas three manganese peroxidase-encoding genes were less affected. On the contrary, highly significant difference was noticed for three cellulolytic genes (cbhI_1, eg1, bgl1) with higher expression levels on the lignocellulose substrate than on glucose. This indicates expression of the wood-attacking degradative enzyme system by the fungus also on the recycled, waste core board material. During the second week of cultivation, ethanol production increased on the core board to 0.24 g/L, and extracellular activities against cellulose, xylan, and lignin were detected. Sugar release from the solid lignocellulose resulted with concomitant accumulation of ethanol as fermentation product. Our findings confirm that the fungus activates its white rot decay system also on industrially processed lignocellulose adopted as growth substrate, and under semi-aerobic cultivation conditions. Thus, P. radiata is a good candidate for lignocellulose-based renewable biotechnology to make biofuels and biocompounds from materials with less value for recycling or manufacturing.

Effect of Chemical Pre-treatments on Bioethanol Production from Chlorella minutissima

In recent years, algal bioethanol production comes into prominence as a trend towards sustainable development. Due to being sustainable energy source and environmental friendly, bioethanol production from algae is becoming increasingly popular all over the world. However, yield of bioethanol production from algae is lower than first generation feedstock's currently, and needs to be improved. In order to increase bioethanol yield, pre-treatments should be performed as cell disruption process on algal biomass. For this reason, researchers investigate the most appropriate pre-treatment method and its parameters for high yield bioethanol production from algae. In this study, cultivated Chlorella minutissima was utilized for bioethanol production. Effects of pre-treatment method (dilute acid and alkaline), chemical concentration, pre-treatment temperature and pre-treatment time on bioethanol yield were investigated. It was found that, the highest bioethanol yield was obtained as 18.52% with acid pre-treatment at pre-treatment temperature of 100 °C and pre-treatment time of 60 minutes.

Anaerobic biodegradation of biofuels and their impact on the corrosion of a Cu-Ni alloy in marine environments

Fuel biodegradation linked to sulfate reduction can lead to corrosion of the metallic infrastructure in a variety of marine environments. However, the biological stability of emerging biofuels and their potential impact on copper-nickel alloys commonly used in marine systems has not been well documented. Two potential naval biofuels (Camelina-JP5 and Fisher-Tropsch-F76) and their petroleum-derived counterparts (JP5 and F76) were critically assessed in seawater/sediment incubations containing a metal coupon (70/30 Cu-Ni alloy). Relative to a fuel-unamended control (1.2 ± 0.4 μM/d), Camelina-JP5 (86.4 ± 1.6 μM/d) and JP5 (77.6 ± 8.3 μM/d) stimulated much higher rates of sulfate reduction than either FT-F76 (11.4 ± 2.7 μM/d) or F76 (38.4 ± 3.7 μM/d). The general corrosion rate (r² = 0.91) and pitting corrosion (r² = 0.92) correlated with sulfate loss in these incubations. Despite differences in microbial community structure on the metal or in the aqueous or sediment phases, sulfate reducing bacteria affiliated with Desulfarculaceae and Desulfobacteraceae became predominant upon fuel amendment. The identification of alkylsuccinates and alkylbenzylsuccinates attested to anaerobic metabolism of fuel hydrocarbons. Sequences related to Desulfobulbaceae were highly enriched (34.2-64.8%) on the Cu-Ni metal surface, regardless of whether the incubation received a fuel amendment. These results demonstrate that the anaerobic metabolism of biofuel linked to sulfate reduction can exacerbate the corrosion of Cu-Ni alloys. Given the relative lability of Camelina-JP5, particular precaution should be taken when incorporating this hydroprocessed biofuel into marine environments serviced by a Cu-Ni metallic infrastructure.

Microalgae-bacteria models evolution: From microalgae steady-state to integrated microalgae-bacteria wastewater treatment models - A comparative review

The search for environmentally neutral alternative fuels had revived the interest for microalgae-bacteria wastewater treatment systems. The potential achieving of bioproducts from microalgae biomass has also greatly contributed. The reactions that occur in these systems are complex, and the degree of scientific knowledge is still scarce compared to that of conventional bacteria wastewater treatments. Mathematical models offer a great opportunity to study the simultaneous effect of the multiple factors affecting microalgae and bacteria, thus allowing for the prediction of final biomass production, and contributing to the system design optimization in terms of operation and control. During the last decades, numerous models describing microalgae growth have been proposed. However, a lower number of integral models considering microalgae as well as bacteria is available. In this paper, the evolution of microalgae models from simple steady-state models (usually dependent on one factor) to more complex dynamic models (with two or more factors) has been revised. A summary of integrated microalgae-bacteria models has been reviewed, outlining their main features and presenting their processes and value parameters. Eventually, a critical discussion on integrated models has been put forward.

Characterization of cellulolytic microbial consortium enriched on Napier grass using metagenomic approaches

Energy grass is a promising substrate for production of biogas by anaerobic digestion. However, the conversion efficiency is limited by the enzymatically recalcitrant nature of cellulosic wastes. In this study, an active, structurally stable mesophilic lignocellulolytic degrading microbial consortium (Np-LMC) was constructed from forest compost soil microbiota by successive subcultivation on Napier grass under facultative anoxic conditions. According to tagged 16S rRNA gene amplicon sequencing, increasing abundance of facultative Proteobacteria was found in the middle of batch cycle which was then subsequently replaced by the cellulose degraders Firmicutes and Bacteroidetes along with decreasing CMCase, xylanase, and β-glucanase activity profiles in the supernatant after 5 days of incubation. Anaerobic/facultative bacteria Dysgonomonas and Sedimentibacter and aerobic bacteria Comamonas were the major genera found in Np-LMC. The consortium was active on degradation of the native and delignified grass. Direct shotgun sequencing of the consortium metagenome revealed relatively high abundance of genes encoding for various lignocellulose degrading enzymes in 23 glycosyl hydrolase (GH) families compared to previously reported cellulolytic microbial communities in mammalian digestive tracts. Enzymes attacking cellulose and hemicellulose were dominated by GH2, 3, 5, 9, 10, 26, 28 and 43 in addition to a variety of carbohydrate esterases (CE) and auxiliary activities (AA), reflecting adaptation of the enzyme systems to the native herbaceous substrate. The consortium identified here represents the microcosm specifically bred on energy grass, with potential for enhancing degradation of fibrous substrates in bioenergy industry.

Heterologous expression and characterization of a new lipase from Pseudomonas fluorescens Pf0-1 and used for biodiesel production

As a kind of important biocatalysts, Pseudomonas lipases are commonly applied in various industrial fields. Pflip1, a new extracellular lipase gene from Pseudomonas. fluorescens Pf0-1, was first cloned and respectively expressed in Escherichia coli BL21(DE3) and Pichia pastoris KM71, the recombinant proteins Pflip1a and Pflip1b were later purified separately. Then Pflip1a was further characterized. The optimum pH of Pflip1a was 8.0 and its optimal temperature was 70 °C. After incubation at 70 °C for 12 h, Pflip1a could retain over 95% of its original activity. It showed the highest activity towards p-nitrophenyl caprylate. Moreover, its activity was profoundly affected by metal ion, ionic surfactants and organic solvents. Furthermore, the two obtained recombinant lipases were immobilized on the magnetic nanoparticles for biodiesel preparation. The GC analysis showed that for the immobilized lipases Pflip1b and Pflip1a, the biodiesel yield within 24 h respectively attained 68.5% and 80.5% at 70 °C. The activities of the two immobilized lipases still remained 70% and 82% after 10 cycles of operations in non-solvent system. These characteristics and transesterification capacity of the recombinant protein indicated its great potential for organic synthesis, especially for biodiesel production.