The goal of this work was to give a comprehensive review on biogas production from microalgae biomass. Different process parameters were summarized in tables which could become comprehensive ...compendium of operation conditions of microalgae preparation for biogas production. Further,, the limitations of the process implementation and commercialization (e.g. high costs of implementation and maintenance, low biomass productivity, limited methane yield due to specific structure of microalgae cell wall) were discussed. It was concluded that the microalgae anaerobic digestion should be incorporated with production of other bioproducts such as biodiesel, bioethanol or volatile fatty acids. Such a biorefinery would open possibility to improve both wastewater treatment and generate valuable products from waste streams.
Methane is an abundant and low-cost gas with high global warming potential and its use as a feedstock can help mitigate climate change. Variety of valuable products can be produced from methane by ...methanotrophs in gas fermentation processes. By using methane as a sole carbon source, methanotrophic bacteria can produce bioplastics, biofuels, feed additives, ectoine and variety of other high-value chemical compounds. A lot of studies have been conducted through the years for natural methanotrophs and engineered strains as well as methanotrophic consortia. These have focused on increasing yields of native products as well as proof of concept for the synthesis of new range of chemicals by metabolic engineering. This review shows trends in the research on key methanotrophic bioproducts since 2015. Despite certain limitations of the known production strategies that makes commercialization of methane-based products challenging, there is currently much attention placed on the promising further development.
•From a wide range of bioproducts synthesized by methanotrophic bacteria the most established are PHAs, methanol and SCP.•Recent progress in the field led to novel methane-based products such as sesquiterpenoids, cadaverine, putrescine.•Low gas-liquid mass transfer and methane uptake remain major technological limitations of methane bioconversions.•Low gas-liquid mass transfer and methane uptake remain major technological limitations of methane bioconversions.
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•Study reports about the utilization of waste office paper for microbial lipid production.•The pretreatment significantly increased the sugar yield without any inhibitors ...formation.•High lipid yield was achieved using waste office paper hydrolysate as feedstock.•Fatty acid profiles of the lipids were similar to the plant/vegetable oils.•Waste paper could be a promising feedstock for biodiesel production at reduced cost.
Waste paper has a potential to serve as renewable feedstock for the biorefineries of fuels, chemicals and materials due to rich in cellulose and its abundance at low cost. In the present study, pretreated waste office paper (WOP) was enzymatically hydrolysed and used for lipid production by Cryptococcus curvatus. The results suggested that the WOP hydrolysate supplemented with ammonium sulphate (2 g/L) and yeast extract (0.5 g/L) as nitrogen source at a C/N ratio of 80 were the most suitable for high yield of lipids. The biomass, lipid yield, lipid content and lipid coefficient achieved from batch cultivation of C. curvatus using untreated and pretreated WOP hydrolysates were 6.32 and 15.20 g/L, 1.39 and 5.75 g/L, 22 and 37.8%, and 99.9 and 234.6 mg/g sugar with the productivity of 0.02 and 0.08 g/L/h, respectively. The fatty acid profile of the lipids indicated that the oleic acid was the major fatty acid followed by palmitic acid, stearic acid and linoleic acid which is quite similar to plant/vegetable oils. Thus, the results suggested that the waste office paper could be an alternative feedstock for production of microbial lipids for biodiesel.
The aim of this study was to evaluate an effect of short and medium chain carboxylic acids (CAs) rich stream derived from acidogenic mixed culture fermentation of acid whey on polyhydroxyalkanoates ...(PHAs) synthesis by Paracoccus homiensis and compare it with the impact of individual synthetic CAs. The obtained results confirmed that the analyzed bacterium is able to metabolize synthetic CAs as the only carbon sources in the growth medium with maximum PHAs production yields of 26% of cell dry mass (CDM). The replacement of the individual CAs by a CAs-rich residual stream was found to be beneficial for the Paracoccus homiensis growth. The highest biomass concentration reached about 2.5 g/L with PHAs content of 17% of CDM. The purified PHAs were identified as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by applying gas chromatography coupled with mass spectrometry, Fourier transform infrared spectroscopic spectra and UV-Vis spectra. Furthermore, a differential scanning calorimetric, thermogravimetric and water contact angle analysis proved that the extracted copolymers have useful properties. The obtained data are promising in the perspective of developing a microbial PHAs production as a part of an integrated valorization process of high CAs content waste-derived streams.
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•The highest total VFAs concentration at RT=5days was achieved at acidic environment.•Alkaline environment was favorable at long RT due to WAS disintegration.•Acetate dominated all of ...the VFAs most likely due to WAS disintegration.•Caproate concentration doubled with prolonging RT from 5 to 15days.
Mixed culture fermentation consists of stable microbial population hence waste could be potentially used as a substrates. The aim of the work was to investigate the impact of pH and retention time on the anaerobic mixed culture fermentation. Trials at different pH (4–12) in unbuffered systems were conducted for 5, 10 and 15days. The highest VFAs concentration was achieved after 15days at pH 10 (0.62g/gVSadded), promising results were also achieved for pH 11 (0.54g/gVSadded). For pH 4 and short retention time propionic acid was the major product instead of acetic acid. For batches run at 15days (besides pH 6) caproic acid presence was noticed whereas at pH 11 occurrence of succinic was quantified. Significant correlation between operational factors and fermentation’s effluents was proved. Throughout changing simple operating parameters one could design process to produce desirable concentration and composition of VFAs.
We present a process model for a lignocellulosic ethanol biorefinery that is open to the biofuels academic community. Beyond providing a series of static results, the wiki-based platform provides a ...dynamic and transparent tool for analyzing, exploring, and communicating the impact of process advances and alternatives for biofuels production. The model is available for download (at
http://econ.jbei.org) and will be updated based on feedback from the community of experts in biofuel-related fields. By making the assumptions and performance metrics of this model transparent, we anticipate this tool can provide a consensus on the energy-related, environmental, and economic performance of lignocellulosic ethanol.
Waste of industrial origin produced from synthetic materials are a serious threat to the natural environment. The ending resources of fossil raw materials and increasingly restrictive legal standards ...for the management of plastic waste have led to research on the use of biopolymers, which, due to their properties, may be an ecological alternative to currently used petrochemical polymers. Polyhydroxyalkanoates (PHAs) have gained much attention in recent years as the next generation of environmentally friendly materials. Currently, a lot of research is being done to reduce the costs of the biological process of PHA synthesis, which is the main factor limiting the production of PHAs on the industrial scale. The volatile fatty acids (VFAs) produced by anaerobic digestion from organic industrial and food waste, and various types of wastewater could be suitable carbon sources for PHA production. Thus, reusing the organic waste, while reducing the future fossil fuel, originated from plastic waste. PHA production from VFAs seem to be a good approach since VFAs composition determines the constituents of PHAs polymer and is of great influence on its properties. In order to reduce the overall costs of PHA production to a more reasonable level, it will be necessary to design a bioprocess that maximizes VFAs production, which will be beneficial for the PHA synthesis. Additionally, a very important factor that affects the profitable production of PHAs from VFAs is the selection of a microbial producer that will effectively synthesize the desired bioproduct. PHA production from VFAs has gained significant interest since VFAs composition determines the constituents of PHA polymer. Thus far, the conversion of VFAs into PHAs using pure bacterial cultures has received little attention, and the majority of studies have used mixed microbial communities for this purpose. This review discusses the current state of knowledge on PHAs synthesized by microorganisms cultured on VFAs.
Microorganisms are responsible for biochemical cycles and therefore play essential roles in the environment. By using omics approaches and network analysis to understand the interaction and ...cooperation within mixed microbial communities, it would be possible to engineer microbiomes in fermentation and digestion reactors to convert organic waste into valuable products.
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•Ionic liquid as catalyst to produce 5-HMF from microcrystalline cellulose was tested.•TMGBF4 was used in 5-HMF production for the first time and confirmed effective.•Microwave ...irradiation as heat source showed superior 5-HMF formation than oil bath.•5-HMF production was optimized by Response Surface Methodology.
Ionic liquid (IL) has been widely investigated in 5-HMF production from biomass. However, most of studies employed IL as reaction solvent which requires a large amount of IL. In the present study, IL was utilized as catalyst in the conversion of microcrystalline cellulose (MCC) to 5-HMF under microwave irradiation (MI) in N,N-dimethylacetamide (DMAc) containing LiCl. 1,1,3,3-tetramethylguanidine (TMG)-based ILs, including 1,1,3,3-tetramethylguanidine tetrafluoroborate (TMGBF4) and 1,1,3,3-tetramethylguanidine lactate (TMGL) which were commonly used in the absorption of SO2 and CO2 from flue gas, were synthesized and applied in the conversion of MCC to 5-HMF for the first time. Of the catalysts employed, TMGBF4 showed high catalytic activity in 5-HMF production from MCC. The condition including the ratio of IL to MCC, temperature and time for MCC conversion was optimized using Central Composite Design (CCD) and Response Surface Methodology (RSM). The highest 5-HMF yield of 28.63% was achieved with the optimal condition.
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