Valuable Bioproducts Research Articles

Flux-Balance Analysis and Mobile CRISPRi-Guided Deletion of a Conditionally Essential Gene in Shewanella oneidensis MR-1.

Carbon-neutral production of valuable bioproducts is critical to sustainable development but remains limited by the slow engineering of photosynthetic organisms. Improving existing synthetic biology tools to engineer model organisms to fix carbon dioxide is one route to overcoming the limitations of photosynthetic organisms. In this work, we describe a pipeline that enabled the deletion of a conditionally essential gene from the Shewanella oneidensis MR-1 genome. S. oneidensis is a simple bacterial host that could be used for electricity-driven conversion of carbon dioxide in the future with further genetic engineering. We used Flux Balance Analysis (FBA) to model carbon and energy flows in central metabolism and assess the effects of single and double gene deletions. We modeled the growth of deletion strains under several alternative conditions to identify substrates that restore viability to an otherwise lethal gene knockout. These predictions were tested in vivo using a Mobile-CRISPRi gene knockdown system. The information learned from FBA and knockdown experiments informed our strategy for gene deletion, allowing us to successfully delete an "expected essential" gene, gpmA. FBA predicted, knockdown experiments supported, and deletion confirmed that the "essential" gene gpmA is not needed for survival, dependent on the medium used. Removal of gpmA is a first step toward driving electrode-powered CO2 fixation via RuBisCO. This work demonstrates the potential for broadening the scope of genetic engineering in S. oneidensis as a synthetic biology chassis. By combining computational analysis with a CRISPRi knockdown system in this way, one can systematically assess the impact of conditionally essential genes and use this knowledge to generate mutations previously thought unachievable.

A Mini-Review: Biowaste-Derived Fuel Pellet by Hydrothermal Carbonization Followed by Pelletizing

This review article focuses on recent studies using hydrothermal carbonization (HTC) for producing hydrochar and its potential application as a solid fuel pellet. Due to the depletion of fossil fuels and increasing greenhouse gas (GHG) emissions, the need for carbon-neutral fuel sources has increased. Another environmental concern relates to the massive amount of industrial processing and municipal solid waste, which are often underutilized and end up in landfills to cause further environmental damage. HTC is an appealing approach to valorizing wet biomass into valuable bioproducts (e.g., hydrochar), with improved properties. In this review, the effects of the main HTC reaction parameters, including reaction temperature, residence time, and feedstock to water ratio on the properties and yield of hydrochar are described. Following this, the pelletizing of hydrochar to prepare fuel pellets is discussed by reviewing the influences of applied pressure, processing time, pellet aspect ratio, moisture content of the hydrochar, and the type and dosage of binder on the quality of the resulting fuel pellet. Overall, this review can provide research updates and useful insights regarding the preparation of biowaste-derived solid fuel pellets.

Heterologous Expression, Characterization, and Comparison of Laccases from the White Rot Causing Basidiomycete Cerrena Unicolor

Lignin is the most abundant renewable source of aromatics on earth, and conversion of it to chemicals and fuels is needed to build an economically viable renewable biofuels industry. Biological routes to converting lignin to fuels and chemicals involve depolymerizing lignin using lignin-degrading enzymes that catalyze the breaking of ether and carbon-carbon bonds in the phenolic and non-phenolic subunits of lignin. Laccases are a crucial class of lignin-degrading enzymes and are copper-containing enzymes capable of oxidizing electron-rich organic substrates such as lignin using molecular oxygen as an electron acceptor. The genome of <em>Cerrena unicolor</em> was recently added to the JGI MycoCosm database and has eight laccases. Two of these laccases, designated Lc1 and Lc2, predicted to have the highest likelihood for successful expression in soluble, active form were selected for characterization. Lc1 and Lc2, which share 65% sequence identity, were heterologously expressed in <em>Komagataella pastoris</em> (formerly <em>Pichia pastoris</em>), allowing characterization and comparison of their purified forms. Lc1 and Lc2 had half-lives of 16 min and 185 min at 60°C, respectively, and, based on molecular dynamics simulations, the longer half-life of Lc2 was due to an increased number and persistence of salt bridges compared to Lc1. Using model lignin-like dimers and a nanostructure-initiator mass spectrometry assay to quantify catalysis of specific bond-breaking events, both Lc1 and Lc2 had their highest activity at pH 3 and in combination with syringaldehyde as a mediator, with Lc1 having a higher catalytic efficiency of β-O-4' ether and C-C bond breaking. This comparative study demonstrates the diversity, including thermostability differences, of laccases from the same fungus, and improves our understanding of laccase catalyzed breaking of bonds commonly found in lignin, which will facilitate the developing this important class of enzymes for applications in the conversion of lignin to valuable bioproducts.

Characterizing sludge pyrolysis by machine learning: Towards sustainable bioenergy production from wastes

Sludge pyrolysis has sparked the interest of researchers because of its capability to dispose of hazardous residues while producing valuable bioproducts. Numerous expensive and laborious experiments are conducted to understand sludge pyrolysis. Machine learning technology can eliminate the need for experimental measurements by systematically learning relationships between variables from historical data. This research aimed to propose a machine learning model to characterize sludge pyrolysis products. A comprehensive database covering various sludge types and pyrolysis reaction conditions was constructed from experimental data. The k-nearest neighbor algorithm was used to reconstruct the missing inputs of sludge composition. The principal component analysis method was then used to decrease dataset dimensionality and acquire relevant information. The obtained scores were normalized and introduced into three machine learning models. The input variables were the chemical properties of sludge and reaction conditions. The response parameters were the distribution and composition of pyrolysis products. Based on descriptive data analysis, the optimum bio-oil yield was obtained at temperatures between 500 and 600 °C. At higher temperatures (700–800 °C), a transition was observed in the product distribution towards more syngas. The random forest regression model showed the highest accuracy among the applied models, with a correlation coefficient higher than 0.813 and a relative mean squared error lower than 12.51. The SHAP analysis using the random forest algorithm was successfully conducted to understand the importance of input variables on output responses. The five top significant features affecting bio-oil yield were ash content, fixed carbon content, operating temperature, and volatile matter content.

Impact of seasons and wastewater cultivation on the biomass and biodiesel production by the Plectonema terebrans BERC10 as a candidate for a multiproduct algal biorefinery

Cyanobacteria offer efficient resource recovery and biotransformation of the wastewater-derived nutrients into valuable bioproducts. However, to achieve commercial robustness, the cultivation potential of the strain must be evaluated under outdoor conditions. The present study evaluated the potential of a filamentous cyanobacterium Plectonema terebrans BERC10 for resource recovery, wastewater treatment, and biomass production for the whole year using an outdoor open-pond cultivation system. The seasonal and nutrient variations had a strong impact on metabolites and biomass production. Accordingly, the maximum biomass production of 1.9 g/L was produced during the summer season (34–42 °C) while 1.7 g/L, 1.554 g/L, and 1.526 g/L biomass was produced during spring, fall, and winter, respectively. The strain adjusted the pH of the wastewater from 7.5 to 11, offering contamination-free cultivation with easier floatation-based harvesting due to its filamentous nature. Besides, wastewater-based outdoor cultivation diverted the metabolic fluxes towards lipid biosynthesis where it accumulated 50–63 % lipids throughout the year. In addition, a maximum of 21 % carbohydrate content was observed during the summer season, while 9.2 %, 13.11 %, and 17 % were measured in the winter, spring, and fall seasons, respectively. The 16–27 % protein content was achieved throughout the year which was shown to be correlated with the varying nitrogen concentration during different seasons. The biomass produced during all four seasons was separately subjected to cascading processing to make the process cost-effective, and 60 % lipids and 25 % proteins were recovered while the residual biomass contained fermentable carbohydrates. Moreover, the strain showed a promising wastewater treatment potential by lowering the total nitrogen by 90 %, total phosphorus by 99 %, total dissolved solids by 70 %, COD by 80 %, and BOD by 85 %. In conclusion, it exhibited remarkable adaptability to the fluctuating environmental conditions, wastewater treatment, and biodiesel production. Further upscaling and techno-economic analyses are the prospects of the study.

Impact of pre-extraction on xylose recovery from two lignocellulosic agro-wastes

A dilute acid hydrolysis of rice husk (RH), wheat straw (WS), and their extractive-free residues was investigated with the objective of recovering the highest yield of xylose while keeping at minimum its conversion into furfural. The hydrolysis conditions were determined for different concentrations of sulfuric acid and different reaction times at 121 °C. The pre-extraction with ethanol-water (1:1, v/v) was also examined as a parameter. Using response surface methodology, the optimum conditions for xylose production were identified as 1.8% of acid and 41.4 min of hydrolysis time for RH, while those for its counterpart EF-RH (extractives-free rice husks) were 1.0% acid concentration, for 60 min. The same conditions were also predicted for WS and its EF-WS. Under these conditions, the xylose yield was 79.6%, 82.8%, 94.3%, and 88.6% for RH, EF-RH, WS, and EF-RW, respectively. Under these conditions the minimal furfural yields obtained were 1.2% and 1.3% for RH and EF-RH, and 0.8% and 1.5%, for WS and EF-WS, respectively. These results suggested that the pre-extraction step before the acid hydrolysis affected, at least in part, the xylose recovery from RH, but it was not necessary for a better xylose yield of WS for its bioconversion into valuable bioproducts like xylitol.

Characterization of the core microbial community governing acidogenic processes for the production of valuable bioproducts

Volatile fatty acids (VFAs) and alcohols generated from acidogenic processes are valuable bioresources. However, how the diversity of acidogenic microorganisms and environmental factors affect their generation are still poorly understood. In this study, 18 different inocula and 42 sludges from acidogenic lab-scale reactors were collected to analyze the microbial communities and their metabolic potential using 16S rRNA genes high throughput sequencing coupled with PICRUSt2. 23 out of 30732 distinctive amplicon sequence variants were identified as the core features and 34.8% of them (e.g., Clostridium spp.) were positively correlated with the generation of the most common product acetate. PICRUSt2 shows that an average of 27% of predicted fermentation-pathway genes was assigned to the core features, suggesting their crucial roles in acidogenesis. From the network aspect, the acidogenic network had a slightly higher number of nodes (12%), but significantly lower numbers of edges (109%) and neighbors (132%) compared with the inoculum network. A total of 28 independent subnetworks from large to small scales were extracted from the acidogenic network. The decentralized distribution of core features in these subnetworks emphasized their non-co-occurring relationships. The electrode potential was the most significant environmental variable (48.2–49.3% of the explanation), positively affecting the distribution of more than 50% of the core features and fermentation pathways. Results of this study emphasized the importance of core features rather than microbial diversity in acidogenic performance and highlighted the response of the core microbial community to environmental changes, which may be applied in practical applications to optimize acidogenic performance.

The Isolation of Specialty Compounds from Amphidinium carterae Biomass by Two-Step Solid-Phase and Liquid-Liquid Extraction.

The two main methods for partitioning crude methanolic extract from Amphidinium carterae biomass were compared. The objective was to obtain three enriched fractions containing amphidinols (APDs), carotenoids, and fatty acids. Since the most valuable bioproducts are APDs, their recovery was the principal goal. The first method consisted of a solid-phase extraction (SPE) in reverse phase that, for the first time, was optimized to fractionate organic methanolic extracts from Amphidinium carterae biomass using reverse-phase C18 as the adsorbent. The second method consisted of a two-step liquid-liquid extraction coupled with SPE and, alternatively, with solvent partitioning. The SPE method allowed the recovery of the biologically-active fraction (containing the APDs) by eluting with methanol (MeOH): water (H2O) (80:20 v/v). Alternatively, an APD purification strategy using solvent partitioning proved to be a better approach for providing APDs in a clear-cut way. When using n-butanol, APDs were obtained at a 70% concentration (w/w), whereas for the SPE method, the most concentrated fraction was only 18% (w/w). For the other fractions (carotenoids and fatty acids), a two-step liquid-liquid extraction (LLE) method coupled with the solvent partitioning method presented the best results.

Impact of composting factors on the biodegradation of lignin in Eichhornia crassipes (water hyacinth): A response surface methodological (RSM) investigation

Water hyacinth (Eichhornia crassipes) is a hydrophyte weed that causes havoc in the aquatic ecosystem as an invasive plant that can obstruct waterways and bring about nutrient imbalance. This study aims to address how this invasive hydrophyte can be physically harvested and biochemically transformed into a bioproduct that can enhance the restoration of damaged soil. Biocomposting, a low-cost biotechnological technique, was designed to degrade the lignocellulosic Eichhornia crassipes biomass and transform it into a valuable bioproduct. The process used response surface methodology (RSM) to investigate the aggregate effect of moisture content, turning frequency, and microbial isolate (Chitinophaga terrae) inoculum size on the breakdown of lignin over 21 days. The moisture content (A), (45, 55, 65) % v/w, inoculum size (B), (5, 7.5, 10)% v/v, and turning frequency (C), (1, 3, 5) days were considered independent variables, while percentage lignin degradation was considered a response variable. The optimal conditions for lignin breakdown were 65.7 percent (v/w) moisture, 7.5 percent (v/v) inoculum concentration, and 5-day interval turning. The R2 score of 0.9733 demonstrates the model's integrity and reliability. Thus, the RSM approach resulted in a fine grain dark brown Nutri-compost that proved effective in enhancing soil fertility. This procedure is recommended for a scale-up process where large quantities of the hydrophyte could be treated for conversion into Nutri compost.

Food waste valorization into bioenergy and bioproducts through a cascade combination of bioprocesses using anaerobic open mixed cultures

This study assessed a strategy for food waste (FW) valorization into multiple products by applying a cascade combination of only two anaerobic processes using open mixed cultures. FWs were firstly subjected to an anaerobic fermentation (AF) to generate an effluent rich in valuable bioproducts. The remaining solid fraction of AF effluent was further valorized into biogas via conventional anaerobic digestion (AD). The operational conditions imposed in AF (55 °C, pH 5.8 and 20.1 d hydraulic retention time) and FW composition promoted a microbial community with high hydrolytic and acidogenic activity that maximized FWs fermentation, resulting in three bioproducts in one single process. pH was a key factor in the microbiome enrichment with Thermoanaerobacterium (63.2% relative abundance). Thermoanaerobacterium was the main bacteria enabling FWs valorization into the three valuable metabolites with remarkable high efficiency, reaching 51.3% bioconversion into SCFAs, 22.8 g L−1 ethanol and 157 L H2 kg VSfed−1. The subsequent AD of the remaining solid fraction resulted in 288.5 L CH4 kg VSfed−1, allowing a final total carbohydrate recovery higher than 80%. This multiproduct strategy enabled FWs valorization by attaining both bioproducts (SCFAs and ethanol) and energy streams (H2 and methane) from a single waste, establishing a groundwork for using open mixed anaerobic cultures for clean and sustainable production of a wide range of added-value compounds.

Tracking of Dissolved Oxygen Distribution and Consumption Pattern in a Bespoke Bacterial Growth System

Microbial cells are used to produce valuable bioproducts. Dense cultures, however, have a high demand for dissolved oxygen which is challenging, considering the low solubility of oxygen in liquid. This study of design and simulation of a gaslift bioreactor highlights a vital limitation of growth, which is the oxygen limitation and sustain aerobic cultures. The aerobic growth has the effect of greatest resource efficiency in that the highest fraction of dosing is done with the largest concentration driving force near critical dissolved oxygen levels and the lowest fraction occurs with near saturated dissolved oxygen values. The results indicate that oxygen homogeneously distributed with limited dead zones at the bottom. The developed system produces 40.5 % more biomass compared with conventional systems, which suffer from oxygen depletion.

Hydrothermal Carbonization of Spent Coffee Grounds for Producing Solid Fuel

Spent coffee grounds (SCG) are industrial biowaste resulting from the coffee-brewing process, and they are often underutilized and end up in landfills, thereby leading to the emission of toxic gases and environmental damage. Hydrothermal carbonization (HTC) is an attractive approach to valorize wet biomass such as SCG to valuable bioproducts (i.e., hydrochar). Thus, in this work, the HTC of SCG was carried out in a 500 L stainless steel vessel at 150, 170, 190, 210, and 230 °C for 30 min, 60 min, 90 min, and 120 min and a feedstock to water weight ratio of 1:5, 1:10, and 1:15, and the use of the resulting hydrochar as a solid fuel was evaluated. The results showed that a high energy recovery (83.93%) and HHV (23.54 MJ/kg) of hydrochar was obtained at moderate conditions (150 °C, 30 min, and feedstock to water weight ratio of 1:5) when compared with conventional approaches such as torrefaction. Following this, the surface morphology, functionality, and combustion behavior of this hydrochar were characterized by SEM, FTIR, and TGA, respectively. In short, it can be concluded that HTC is an effective approach for producing solid fuel from SCG and the resulting hydrochar has the potential to be applied either in domestic heating or large-scale co-firing plants.

Genomic analysis of heavy metal-resistant Halobacterium salinarum isolated from Sfax solar saltern sediments

The draft genome sequences of five archaeal strains, isolated from Sfax solar saltern sediments and affiliated with Halobacterium salinarum, were analyzed in order to reveal their adaptive strategies to live in hypersaline environments polluted with heavy metals. The genomes of the strains (named AS1, AS2, AS8, AS11, and AS19) are found to contain 2,060,688; 2,467,461; 2,236,624; 2,432,692; and 2,428,727 bp respectively, with a G + C content of 65.5, 66.0, 67.0, and 66.2%. The majority of these genes (43.69–55.65%) are annotated as hypothetical proteins. Growth under osmotic stress is possible by genes coding for potassium uptake, sodium efflux, and kinases, as well as stress proteins, DNA repair systems, and proteasomal components. These strains harbor many genes responsible for metal transport/resistance, such as: copper-translocating P-type ATPases, ABC transporter, and cobalt-zinc-cadmium resistance protein. In addition, detoxification enzymes and secondary metabolites are also identified. The results show strain AS1, as compared to the other strains, is more adapted to heavy metals and may be used in the bioremediation of multi-metal contaminated environments. This study highlights the presence of several commercially valuable bioproducts (carotenoids, retinal proteins, exopolysaccharide, stress proteins, squalene, and siderophores) and enzymes (protease, sulfatase, phosphatase, phosphoesterase, and chitinase) that can be used in many industrial applications.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00792-022-01273-0.

Phosphate-inducible poly-hydroxy butyrate production dynamics in CO2 supplemented upscaled cultivation of engineered Phaeodactylum tricornutum

Diatoms such as Phaeodactylum tricornutum are emerging as sustainable alternatives to traditional eukaryotic microbial cell factories. In order to facilitate a viable process for production of heterologous metabolites, a rational genetic design specifically tailored to metabolic requirements as well as optimised culture conditions are required. In this study we investigated the effect of constitutive and inducible expression of the heterologous poly-3-hydroxybutyrate (PHB) pathway in P. tricornutum using non-integrative episomes in 3 different configurations. Constitutive expression led to downregulation of at least one individual gene out of three (phaA, phaB and phaC) and was outperformed by inducible expression. To further asses and optimise the dynamics of PHB accumulation driven by the inducible alkaline phosphatase 1 promoter, we upscaled the production to lab-scale bioreactors and tested the effect of supplemented CO2 on biomass and PHB accumulation. While ambient CO2 cultivation resulted in a maximum PHB yield of 2.3% cell dry weight (CDW) on day 11, under elevated CO2 concentrations PHB yield peaked at 1.7% CDW on day 8, coincident with PHB titres at 27.9 mg L−1 that were approximately threefold higher than ambient CO2. With other more valuable bio-products in mind, these results highlight the importance of the genetic design as well as substrate availability to supply additional reduction equivalents to boost biomass accumulation and relieve potential enzymatic bottlenecks for improved product accumulation.

Efficient multiplex CRISPR/Cpf1 (Cas12a) genome editing system in Aspergillus aculeatus TBRC 277

CRISPR/Cas technology is a versatile tool for genome engineering in many organisms, including filamentous fungi. Cpf1 is a multi-domain protein of class 2 (type V) RNA-guided CRISPR/Cas endonuclease, and is an alternative platform with distinct features when compared to Cas9. However, application of this technology in filamentous fungi is limited. Here, we present a single CRISPR/Cpf1 plasmid system in Aspergillus aculeatus strain TBRC 277, an industrially relevant cell factory. We first evaluated the functionality of three Cpf1 orthologs from Acidaminococcus sp. BV3L6 (AsCpf1), Francisella tularensis subsp. novicida U112 (FnCpf1), and Lachnospiraceae bacterium (LbCpf1), in RNA-guided site-specific DNA cleavage at the pksP locus. FnCpf1 showed the highest editing efficiency (93%) among the three Cpf1s. It was further investigated for its ability to delete a 1.7kb and a 0.5kb from pksP and pyrG genes, respectively, using two protospacers targeting these gene loci in a single crRNA array. Lastly, simultaneous editing of three sites within TBRC 277 genome was performed using three guide sequences targeting these two genes as well as an additional gene, kusA, which resulted in combined editing efficiency of 40%. The editing of the NHEJ pathway by targeting kusA to generate a NHEJ-deficient strain of A. aculeatus TBRC 277 improved gene targeting efficiency and yielded more precise gene-editing than that of using wild-type strain. This promising genome-editing system can be used for strain improvement in industrial applications such as production of valuable bioproducts.

Utilization of lignocellulosic biofuel conversion residue by diverse microorganisms

BackgroundLignocellulosic conversion residue (LCR) is the material remaining after deconstructed lignocellulosic biomass is subjected to microbial fermentation and treated to remove the biofuel. Technoeconomic analyses of biofuel refineries have shown that further microbial processing of this LCR into other bioproducts may help offset the costs of biofuel generation. Identifying organisms able to metabolize LCR is an important first step for harnessing the full chemical and economic potential of this material. In this study, we investigated the aerobic LCR utilization capabilities of 71 Streptomyces and 163 yeast species that could be engineered to produce valuable bioproducts. The LCR utilization by these individual microbes was compared to that of an aerobic mixed microbial consortium derived from a wastewater treatment plant as representative of a consortium with the highest potential for degrading the LCR components and a source of genetic material for future engineering efforts.ResultsWe analyzed several batches of a model LCR by chemical oxygen demand (COD) and chromatography-based assays and determined that the major components of LCR were oligomeric and monomeric sugars and other organic compounds. Many of the Streptomyces and yeast species tested were able to grow in LCR, with some individual microbes capable of utilizing over 40% of the soluble COD. For comparison, the maximum total soluble COD utilized by the mixed microbial consortium was about 70%. This represents an upper limit on how much of the LCR could be valorized by engineered Streptomyces or yeasts into bioproducts. To investigate the utilization of specific components in LCR and have a defined media for future experiments, we developed a synthetic conversion residue (SynCR) to mimic our model LCR and used it to show lignocellulose-derived inhibitors (LDIs) had little effect on the ability of the Streptomyces species to metabolize SynCR.ConclusionsWe found that LCR is rich in carbon sources for microbial utilization and has vitamins, minerals, amino acids and other trace metabolites necessary to support growth. Testing diverse collections of Streptomyces and yeast species confirmed that these microorganisms were capable of growth on LCR and revealed a phylogenetic correlation between those able to best utilize LCR. Identification and quantification of the components of LCR enabled us to develop a synthetic LCR (SynCR) that will be a useful tool for examining how individual components of LCR contribute to microbial growth and as a substrate for future engineering efforts to use these microorganisms to generate valuable bioproducts.

Advanced technologies on the sustainable approaches for conversion of organic waste to valuable bioproducts: Emerging circular bioeconomy perspective

Rapid population growth and other human activities have generated massive waste from various sectors in recent decades. Studies revealed that by 2050, global solid waste generation is expected to reach 70% to 3.4 billion metric tons. Thus, the authorities urgently need to provide a low-cost, efficient technology for treating waste disposal. However, it is evident that only 20% of waste is recycled, and the remaining is still being considered for landfilling. In developing countries, the generated waste is simply disposed of in an open area, which causes a severe threat to humans, animals, and the environment. To date, organic waste and fourth-generation biomass have been investigated for multiple targeted products. Thus, the present review article highlights the emerging problems in organic waste generation, management, and converting them into various value-added bioproducts. This review also deals with the conversion of multiple biofuels such as liquid, solid, gaseous, and bioelectricity from organic waste resources. Besides, the latest approaches in organic waste are also detailly addressed for the production of value-added bioproducts such as bioplastic, bio-compost, and organic acids. Furthermore, the techno-economic analysis (TEA) and life cycle assessment (LCA) of organic waste is also explored. The transformation of organic waste to value-added bioproducts enhances the circular bioeconomy approach by reducing waste, increasing energy production, and other healthcare products. Finally, it is concluded that the utilization of organic waste to value-added bioproducts and biofuels production will be helpful in achieving high energy security, environmental protection, as well as enhancing the bioeconomy perspective.

Environmental life cycle assessment of spent coffee ground pellet

Coffee, the most globally prevalent beverage, entails environmental and economic consequences due to the high content of toxic compounds in leftover from brewing. Waste-to-energy technologies propose recovering energy from solid or liquid wastes via various treatment methods. This study investigates the environmental performance of the spent coffee ground application in pellet production as a valuable bio-product by life cycle assessment. System boundaries comprise four stages: (1) spent coffee ground collection; (2) pellet production; (3) thermal energy generation; and (4) waste disposal. The LCA model is interpreted by ReCipe 2016 in both midpoint and endpoint levels per 1 MJ of thermal energy as functional unit. Alternative waste-to-energy approaches into transesterification, pyrolysis, and direct combustion of spent coffee ground are also assessed. The impact assessment shows that the pelletizing process significantly contributes to all impact categories except ozone formation and terrestrial ecotoxicity, which is influenced primarily by the transportation process in the spent coffee ground collection stage. The spent coffee ground pellet can lead to climate change mitigation, and reduction in freshwater eutrophication and use of resources due to credits from ash disposed to landfill.Biodiesel is the worst potential option among alternative scenarios, while pellet production and bio-oil demonstrate the most favorable environmental profiles for all impact categories. Damage assessment indicates that pellet production and alternative scenarios mainly influence human health.

Soft elastic tubular reactor: An unconventional bioreactor for high-solids operations

Many bioreactors for solid state (SSF) and high-solids load fermentations have been developed in order to obtain valuable bioproducts. In general, it is emphasized the necessity for design improvements in reactor mixing, heat transfer, and gaseous mass transfer. A soft-elastic tubular reactor (SETR) was built and its behavior in terms of aeration, mixing, and temperature control was evaluated. Although soft-elastic reactors have been explored for some time, this was the first time they were thoroughly investigated for fermentation use. Depending on the applied parameters, such as aeration, mixing rate, and media characteristics (liquid viscosity, solid, sludge), KLa ranged between 1 and 40 h−1, a well-mixed state was attained between 0.3 and 60 min, and the temperature reached operational stability within 20 min. Soybeans were fermented by Bacillus subtilis subsp. natto as a proof of concept (moisture content from 66 wt% up to 80 wt%). The proposed SETR demonstrated that temperature, mixing, and aeration could be modified to meet the needs of the process, and while more research is needed, it might be regarded as a new option for solid state or high-load substrate processes.

An Approach to Correlate Chemical Pretreatment to Digestibility Through Biomass Characterization by SEM, FTIR and XRD

A comprehensive study was carried out to assess the efficiency of different chemicals on the pretreatment of plant biomass, corn cobs. The efficiency was assessed based on its effect on subsequent hydrolysis of biomass for the conversion to fermentable sugars. Both alkali- and acid-based pretreatments were carried out under optimized conditions to avoid the formation of inhibitors and also to yield more sugars. Among the different chemicals used, 2% NaOH (w/v) was found to be effective with the delignification efficiency of 84.32%, and furthermore, the biomass saccharification efficiency was found to be 86.28% using 1.20% (v/v) HNO3 at 100°C for 90 min, whereas the pretreatment with other chemicals such as KOH, NaClO2, Na2SO3, and NH3 had significantly (p < 0.05) low delignification, which ultimately reduced the saccharification efficiency. In acid–base-based pretreatment, 1.5% (v/v) HNO3 resulted in 63.42% delignification along with 68% digestion of hemicelluloses. The effect of pretreatment efficiency on digestibility was investigated by biomass characterization using SEM, FTIR, and XRD analyses before and after the treatment process. The imaging studies clearly indicated that 2% NaOH efficiently digested the complex matrix alignment and enhanced the surface area of the carbohydrate polymer which had shown a positive impact on the rate of hydrolysis. The study concludes that alkali-based pretreatment is the efficient and cost-viable technique for the effective valorization of corn cobs for the production of fermentable sugars which can be further converted to various valuable bioproducts.