80 research outputs found
Biovalorization of Lignocellulosic Waste
No full textThe swift and successful transition towards a fossil fuel-free economy is amongst the most complex challenges ever faced by humanity, implicating intricate connections and trade-offs with the so-called water–energy–food nexus [...
Microbial protein production from sulfide-rich biogas through an enrichment of methane- and sulfur-oxidizing bacteria
No full textThis study evaluated the possibility of combining methane oxidizing bacteria (MOB) with sulfur oxidizing bacteria (SOB) to enable the utilization of sulfide-rich biogas for microbial protein production. For this purpose, a MOB-SOB mixed-culture enriched by feeding both methane and sulfide was benchmarked against an enrichment of solely MOB. Different CH4:O2 ratios, starting pH values, sulfide levels and nitrogen sources were tested and evaluated for the two enrichments. The MOB-SOB culture gave promising results in terms of both biomass yield (up to 0.07 ± 0.01 g VSS/g CH4-COD) and protein content (up to 73 ± 5% of VSS) at 1500 ppm of equivalent H2S. The latter enrichment was able to grow also under acidic pH (5.8-7.0), but as inhibited outside the optimal CH4:O2 ratio of 2:3. The obtained results show the capability of MOB-SOB mixed-cultures to directly upcycle sulfide-rich biogas into microbial protein potentially suited for feed, food or biobased product applications
Valorisation of industrial hemp (Cannabis sativa L.) residues and cheese whey into volatile fatty acids for single cell protein production
No full textThe production of single cell protein (SCP) using lignocellulosic materials stands out as a promising route in the circular bioeconomy transition. However, multiple steps are necessary for lignocellulosics-to-SCP processes, involving chemical pretreatments and specific aerobic cultures. Whereas there are no studies that investigated the SCP production from lignocellulosics by using only biological processes and microbial biomass able to work both anaerobically and aerobically. In this view, the valorisation of industrial hemp (Cannabis sativa L.) biomass residues (HBRs), specifically hurds and a mix of leaves and inflorescences, combined with cheese whey (CW) was investigated through a semi-continuous acidogenic co-fermentation process (co-AF). The aim of this study was to maximise HBRs conversion into VFAs to be further used as carbon-rich substrates for SCP production. Different process conditions were tested by either removing CW or increasing the amount of HBRs in terms of VS (i.e., two and four times) to evaluate the performance of the co-AF process. Increasing HBRs resulted in a proportional increase in VFA production up to 3115 mg HAc L−1, with experimental production nearly 40% higher than theoretical predictions. The synergy between HBRs and CW was demonstrated, proving the latter as essential to improve the biodegradability of the former. The produced VFAs were subsequently tested as substrates for SCP synthesis in batch aerobic tests. A biomass concentration of 2.43 g TSS L−1 was achieved with a C/N ratio of 5.0 and a pH of 9.0 after two days of aerobic fermentation, reaching a protein content of 42% (g protein per g TSS). These results demonstrate the overall feasibility of the VFA-mediated HBR-to-SCP valorisation process
H2S-laden biogas triggers sulfur amino acids production in microbial protein synthesized during mixed culture fermentation by methane and sulfur oxidizing bacteria
No full textOn-site nitrogen and carbon upcycling from anaerobic digestion through microbial protein production: a case study
No full textAnaerobic digestion plays a central role in the context of resource recovery from wastewater. Due to the availability of carbon and nutrients (N, P) in the form of biogas and digestate, innovative biorefinery approaches can be implemented to upgrade these fundamental building blocks directly into new high-value bioproducts such as microbial protein. Both methane- and hydrogen-oxidizing bacteria offer a potential for clean-tech on-site C and N upcycling through microbial protein production. The present study compares these two platforms by evaluating their potential in the framework of an ideal future wastewater biorefinery
Planck-scale-modified dispersion relations in FRW spacetime
No full textIn recent years, Planck-scale modifications of the dispersion relation have been attracting increasing interest also from the viewpoint of possible applications in astrophysics and cosmology, where spacetime curvature cannot be neglected. Nonetheless, the interplay between Planck-scale effects and spacetime curvature is still poorly understood, particularly in cases where curvature is not constant. These challenges have been so far postponed by relying on an ansatz, first introduced by Jacob and Piran. We propose here a general strategy of analysis of the effects of modifications of the dispersion relation in Friedmann-Robertson-Walker spacetimes, applicable both to cases where the relativistic equivalence of frames is spoiled (“preferred-frame scenarios”) and to the alternative possibility of “DSR-relativistic theories,” theories that are fully relativistic but with relativistic laws deformed so that the modified dispersion relation is observer independent. We show that the Jacob-Piran ansatz implicitly assumes that spacetime translations are not affected by the Planck scale, while under rather general conditions, the same Planck-scale quantum-spacetime structures producing modifications of the dispersion relation also affect translations. Through the explicit analysis of one of the effects produced by modifications of the dispersion relation, an effect amounting to Planck-scale corrections to travel times, we show that our concerns are not merely conceptual but rather can have significant quantitative implications
Biowaste upcycling into second-generation microbial protein through mixed-culture fermentation
No full textSecuring a sustainable protein supply at the global level is among the greatest challenges currently faced by humanity. Alternative protein sources, such as second-generation microbial protein (MP), could give rise to innovative circular bioeconomy practices, synthesizing high-value bioproducts through the recovery and upcycling of resources from overabundant biowastes and residues. Within such a multi-feedstock biorefinery scenario, the wide range of microbial pathways and networks that characterize mixed microbial cultures, offers interesting and not yet fully explored advantages over conventional monoculture-based processes. In this review, we combine a comprehensive analysis of waste recovery platforms for second-generation MP production with a critical evaluation of the research gaps and potentials offered by mixed culture-based MP fermentation processes
From residue to resource: The multifaceted environmental and bioeconomy potential of industrial hemp (Cannabis sativa L.)
No full textIn the emerging context of circular bioeconomy, industrial hemp (Cannabis Sativa L.) biomass is a valuable resource for the sustainable implementation of second-generation biorefineries. Potentially, all the main hemp components can find application within different biorefinery approaches, adding value to the conventional production of hemp fibres and seeds. Hurds, leaves and inflorescences, constituting most of the hemp plant biomass, and often considered as low-value residues, can indeed play a key role in the sustainable production of both bioenergy and high-value bioproducts. The present article reviews the advances and outlines the potential future perspectives of hemp-based biorefineries. After critically overviewing some of the most established applications of hemp, spanning from soil bioremediation to bioenergy and biofuel production, particular attention is given to novel valorisation schemes to synthetize highly demanded bioproducts such as microbial protein and biopolymers. Our preliminary calculations show that hemp biomass can sustain high biodiesel yield (1.6 g/g VS (volatile solids)) and related revenues (510–868 €/ha•year), while bioethanol production can yield 0.10–0.33 mL/g VS, profiting between 75–325 €/ha•year. Moreover, hemp suits biomethane production by yielding and profiting 98–426 mL/g VS and 60–380 €/ha•year, respectively. High yields of polyhydroxybutyrate (0.13 g/g VS) can be obtained, albeit high production costs might restrain their marketability. Finally, the biomethane-to-microbial protein pathway can yield and profit 0.03–0.15 g/g VS and 141–893 €/ha•year, respectively, while the volatile fatty acids-to-microbial protein pathway 0.04 g/g VS and 91–362 €/ha•year
Sulfur-containing microbial protein production from sulfide-rich biogas in hollow fiber membrane bioreactors
No full textAnaerobic digestion of organic waste can unlock the upcycling of waste resources through the valorization of biogas into value-added products. This study proposed the conversion of sulfide-rich biogas into microbial protein (MP) through a microbial fermentation process carried out in hollow fiber membrane bioreactors by means of a consortium of methane- and sulfur-oxidizing bacteria, characterized by the dominance of Methylocystis spp. and Chryseobacterium spp. The efficiency of the gas-to-liquid mass transfer and the effects of biofilm formation on gas diffusion, as well as the effects of gas loading rate (10 L/d and 15 L/d) and sulfide content of the biogas (1500, 3000 and 4000 ppm of H2S) on the fermentation performance were evaluated. Biomass concentrations up to 768.5 (± 17.2) mg of volatile suspended solids (VSS) per liter were achieved when treating biogas containing 1500 ppm of H2S. Increasing sulfide concentrations (up to 4000 ppm of H2S) had negligible effects on the biomass productivity and yield. The biomass had a high protein (up to 64.7 %) and amino acids (up to 510.3 mg/g VSS) content, with beneficial effects of H2S on the content of sulfur-containing amino acids. Switching from 1500 ppm to 4000 ppm of H2S increased the content of methionine and cysteine by 57 % and 39 %, respectively
Valorisation of industrial hemp (Cannabis sativa L.) biomass residues through acidogenic fermentation and co-fermentation for volatile fatty acids production
No full textIn line with the emerging circular bioeconomy paradigm, the present study investigated the valorisation of abundant hemp biomass residues (HBRs) such as hurds (HH) and a mix of leaves and inflorescences (Mix), and other organic wastes (i.e., cheese whey and grape pomace) through the volatile fatty acid (VFA) production in mono- and co-acidogenic fermentation. The highest VFA yields, measured as acetic acid (HAc) per unit of volatile solids (VS), were obtained with the untreated Mix in mono-fermentation (185±57 mg HAc/g VS) and with the combination of Mix and CW in co-fermentation (651±65 mg HAc/g VS), while the highest HAc percentage reached up to 94% of total VFAs. Finally, a preliminary techno-economic evaluation revealed that the mono-fermentation of alkali pretreated HH could lead to the highest revenues among HBRs, reaching up to 710-1810, 618-1577 and 766-3722 €/ha∙year for the production of HAc, single cell protein and polyhydroxybutyrates, respectively
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