MAIN RESEARCH ACTIVITIES

Biodiesel production by microalgae

Butanol production by fermentation of Clostridium acetobutylicum

Biosorption of dyes

Carbon capture and storage by biomimetic absorption

Hydrodynamics of gas-liquid units

Granulation in gas fluidized bed

Gas-solids fluidization

Biodiesel production by microalgae

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Biofuel production coupled with carbon dioxide sequestration by means of photosynthetic microorganisms has been considered as a promising process since the end of the last century. In particular, microalgae biomass may be burned/gasified as crude dry matter in combustors/gasifiers or may be processed to produce liquid fuels. In the latter case, bio-oil is extracted from microalgae and it may be adopted either as crude fuel or transesterified to biodiesel.

Microalgae strains are from the ACUF collection of the Biological Science Department at the Università degli Studi di Napoli Federico II.

Lab-scale Photobioreactors

Main results

Stichococcus strains have been screened to select the most promising for biofuel production
S. bacillaris 158/11 proved to be the best strain to produce biodiesel
Photosynthetic efficiency of the process was assessed
Specific biomass productivity was ~60 mg_DM/(L•day) under the semi-continuous conditions tested.
Total lipid productivity was 14 mg/(L•day) at a dilution rate of 0.050 1/day under the semi-continuous conditions tested.
Preliminary techno-economic assessments of the biodiesel production were carried out

Current research

Characterization of microalgae growth, characterization of metabolites (lipid fraction) and their distribution as a function of the operating conditions
Development and characterization of photobioreactors
Simulation of tubular photobioreactor (see Hydrodynamics of gas-liquid units)
Techno-economic assessment of the process

Butanol production by fermentation of Clostridium acetobutylicum

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Acetone-Butanol-Ethanol (ABE) production by Clostridium acetobutylicum used to be a major bioprocess until the mid-20^th century when the petrochemical route to butanol made it cost-ineffective. The recent developments in several scientific/technological fields made the ABE fermentation process competitive with respect to the petrochemical routes for solvents production.

Two pathways have been identified in the metabolism of clostridia strains: acidogenesis, characterized by substrate conversion into acids (acetic and butyric acids) by high motile cells (acidogenic cells); solventogenesis, characterized by substrate and acid conversion into solvents (ABE) by clostridial cells unable to grow (solventogenic cells). The shift between the two pathways strongly depends on pH and concentration of metabolites
.

Main results

ABE production by lactose fermentation
Assessment of the growth kinetics of acidogenic cells of Clostridium acetobutylicum DSM 79
Butanol production process by immobilized Clostridium acetobutylicum a continuous Packed Bed Reactor (PBR) using Tygon® rings as carrier. The optimal performance of the reactor was recorded at dilution rate of 0.97 1/h: the butanol productivity was 4.4g/Lh and the selectivity in butanol was 88%_w.

Biofilm fixed bed reactor operated
under continuous conditions

Current research

Characterization of solvent production rate
Development of continuous biofilm reactors characterized by high performances
Butanol production through fermentation of cheese whey by C. acetobutylicum
Techno-economic assessment of the process
Characterization of C. acetobutylicum fermentation using pentose and/or hesose sugars as substrates

Biosorption of dyes

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Recently, biomasses form fungal cultures have been assessed as potential sorbent materials. Tests with Cunninghamella elegans biomass revealed large adsorption capacity against dyes commonly used in textile industries. Collaboration with Plant Biology Department at Università degli Studi di Torino started in 2010 for the assessment of biosorption of dyes on fungal biomasses having different pretreatment, particularly drying or lyophilisation.

Main results

Characterization of kinetics and equilibrium of adsorption on lyophilized biomass of Cunninghamella elegans MUT 2861 of reference dyes.
Characterization of kinetics and equilibrium of adsorption on lyophilized biomass of C. elegans MUT 2861 of wastewaters from textile industries.
Preliminary design of bio-adsorbers.
Preliminary assessment of biosorption in fluidized bed of lyophilized biomass of C. elegans MUT 2861.

Current research

Characterization of kinetics and equilibrium of dyes adsorption on dried biomass of C. elegans MUT 2861.
Preliminary assessment of biosorption in fluidized bed of dried biomass of C. elegans MUT 2861

Carbon capture and storage by biomimetic absorption

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In the framework of Carbon Capture and Storage (CCS) processes, the absorption into aqueous amine solutions is the most advanced process for post-combustion treatments. Drawback related with pollution issues due to amines use may be avoided using environmental friendly additives to enhance CO₂ absorption rate into aqueous phase. Carbonic anhydrase is an ubiquitous enzyme able to atalysed CO₂ hydration up to 106 times faster than the spontaneous reaction. Biomimetic approach to CO₂ capture is based on the adoption of carbonic anhydrase as catalyst into CCS plants.

Main results

Feasibility assessment of biomimetic absorption process to capture CO₂ from flue gas of thermal power plants (collaboration with ENEL Ingegneria & Innovazione)
Long term stability at high temperature of recombinant carbonic anhydrase from the thermophile bacterium Sulfurihydrogenibium sp. (collaboration with Istituto di Biochimica delle Proteine at CNR and Centro Interdipartimentale Biomateriali at Università degli Studi di Napoli Federico II)

Current research

Characterization of kinetics of recombinant anhydrase through CO₂ absorption tests into alkaline solutions
Immobilization of carbonic anhydrase on solid supports for CO₂ capture purposes

Hydrodynamics of gas-liquid units

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The research develops along two lines: experimental investigation and CFD simulation.
The experimental investigation regards the hydrodynamics of bubble columns (BCs) and internal loop airlifts (ILAs). The attention is focused on the effects of features of the liquid - superficial tension and viscosity for Newtonian fluids, and relaxation time for Non-Newtonian fluids – and unit design on the hydrodynamic regimes.
CFD simulation is focused on local flow structures of bubble columns.

Main results

Newtonian fluids: the superficial gas velocity at the transition between hydrodynamic regimes (homogenous regime – vortical-spiral regime – heterogeneous regime) as a function the liquid viscosity was characterized by a maximum.
Newtonian fluids: the maximum stable gas hold-up and gas-liquid mass transfer coefficient in BC as a function the liquid viscosity was characterized by a maximum.
Newtonian fluids: homogeneous regime stability enhances for viscosity < 4.25 mPa•s, in BC, and for viscosity < 7.68 mPa•s, in ILA.
Non-Newtonian fluids: the transition velocity the superficial gas velocity at the transition between hydrodynamic regimes (homogenous regime – vortical-spiral regime – heterogeneous regime) increases with liquid elasticity.

Current research

Combined effects of superficial tension and viscosity of Newtonian fluids on hydrodynamics of BC and ILA.
Systematic investigation of effects of liquid elasticity (Non-Newtonian fluids) on hydrodynamics of BC and ILA.
Simulation of liquid flow structures in a BC

Granulation in gas-fluidized beds

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Characterization of the particle size distribution in gas-fluidized bed.
Modelling of granulation in gas-fluidized bed.

Gas-solids fluidization

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The research develops along two lines: characterization of fluidized bed of assorted solids, and continuous separation of components of solid mixtures.
The characterization of fluidized bed of assorted solids regards: i) experimental investigation in both cylindrical columns and tapered columns; ii) CFD simulation of gas-solids behaviour.
The separation of components of solid mixtures is carried out in a tapered column operated under selected operating conditions.