Gate-to-gate life cycle assessment of biosurfactants and bioplasticizers production via biotechnological exploitation of fats and waste oils

BACKGROUND: This study investigated the biotransformation of fats and waste oils towards glycolipid biosurfactants and bioplasticizers. The ecological performance and environmental impacts of the bioprocesses were evaluated aiming to assess their present environmental status and thus suggest future improvements using LCA methodology. RESULTS: Biosurfactants, namely rhamnolipids and sophorolipids were obtained via fermentation. Bioplasticizers, Fatty Acid Ethyl Esters (FAEE) and Monoglycerides (MAG), were developed via enzymatic catalysis with selected enzymes in mesophilic temperatures via ethanolysis and glycerolysis, respectively. The study revealed that air emissions, electricity and thermal energy requirements are the key contributors to the potential environmental impacts in the LCIA. More specifically, rhamnolipids production has less energetic needs compared to sophorolipids manufacturing, resulting thus to lower environmental impacts. The increased thermal requirements of MAG production phase is the main contributor to their negative environmental performance, with the overall energy consumption for MAG production being 3-fold higher than the FAEE formation phase. CONCLUSIONS: The assessment identified that among the biosurfactant production processes, the sophorolipids production resulted to 22.7% higher environmental impact compared to rhamnolipids. Similarly, FAEE production can be classified as a more environmental friendly process compared to MAG, resulting to 67% lower environmental impact based on the environmental indicators assessed

Effects of Burkholderia thailandensis rhamnolipids on the unicellular algae Dunaliella tertiolecta

The effects of rhamnolipids (RLs) produced and further purified from Burkholderia thailandensis, on the unicellular microalgae Dunaliella tertiolecta were investigated, in terms of RLs ability to affect algal growth, photosynthetic apparatus structure and energy flux, round and through photosystems II and I. Specifically, 24–48 h RLs-treated algae (RLs at concentrations ranged from 5 to 50 mg L−1) showed significantly decreased levels of growth rate, while increased levels of Chl a and b were obtained only in 72–96 h RLs-treated algae. Similarly, although no changes were obtained in the Chl a/b ratio and almost all chlorophyll fluorescence parameters over time, yields of electron transport (ϕR0, ϕE0) and respective performance index (PItotal) were negatively affected at 72 and 96 h. Based on those findings, it seems that the inhibitory effect of RLs on the algae growth rate after 24 and 48 h and the gradual attenuation of the phenomenon (after 72 h of exposure), may indicate the initial response of the organism, as well as algae ability to overcome, since RLs showed no effects on algae photosynthetic ability. Those findings reveal for the first time that RLs from Burkholderia thailandensis are not harmful for Dunaliella tertiolecta. However, further studies with the use of more aquatic species could be essential for assessing the RLs-mediated effects on aquatic biota

Chlorella vulgaris as a green biofuel factory : comparison between biodiesel, biogas and combustible biomass production

Biofuels are viewed as the answer to safeguard the currently challenged energy security. To this end, the present study provides a comparison between approaches regarding microalgal biomass conversion to bioenergy, with a view on sustainable implementation. The energetic valorization of Chlorella vulgaris biomass cultivated under heterotrophic, sulfur-limited conditions was investigated through the biofuels biodiesel, biogas (biomethane) and combustible dry biomass. The lipid productivity can reach the value of 442.9 6.5 mg L-1 d(-1) containing suitable fatty acids for biodiesel production. Next, biochemical methane potential (BMP) assays yielded 360.9 20.2 mL CH4 g VSadlded under mesophilic conditions, while the calorific value of dry C. vulgaris biomass was measured as 24,538 182 kJ kgpw(-1) (5,865 43 kcal kgpw(-1)). Considering the downstream processing required in each approach, the most promising energy valorization method is anaerobic digestion able to reach values up to 20,862 kJ Lreactor 1 day(-1) in continuous systems

KINETIC MODELLING OF PSEUDOMONAS DENITRIFICANS GROWTH AND OPTIMIZATION OF DENITRIFICATION PROCESSES

DENITRIFICATION IS THE BIOLOGICAL PROCESS WHICH IS RESPONSIBLE FOR THE REMOVAL OF NITROGEN IN THE FORM OF NITRATE AND /OR NITRITE FROM POTABLE WATER OR WASTEWATERS BY CONVERSION TO NITROGEN GAS. THE PROCESS IS CARRIED OUT BY HETEROTROPHIC FACULTATIVE AEROBIC BACTERIA UNDER ANOXIC CONDITIONS. A MATHEMATICAL MODEL CAPABLE OF DESCRIBING ACCURATELY THE MICROORGANISM'S GROWTH RATE AND THE RATE OF DENITRIFICATION UNDER AEROBIC, ANOXIC AND TRANSIENT CONDITIONS OF GROWTH, IS NECESSARY FOR THE DENITRIFICATION PROCESS DESIGN. KINETIC DATA FOR THE ESTABLISHMENT OF SUCH A MODEL WERE TAKEN FROM BATCH EXPERIMENTS WITH A PURE CULTURE OF A REPRESENTATIVE DENITRIFYING BACTERIUM (PSEUDOMONAS DENITRIFICANS) IN A DEFINED SYNTHETIC MEDIUM. CONSIDERING THE BIOLOGICAL REDUCTION OF NITRATESTO MOLAR NITROGEN AS A TWO-STEP PROCESS (PRODUCTION OF NITRITE-NITROGEN AS ANINTERMEDIATE), AN OVERALL DENITRIFICATION MODEL WAS DEVELOPED THAT WAS USED FOR THE OPTIMUM DESIGN OF CSTR AND SBR REACTORS. DENITRIFICATION, WAS ALSO CONSIDERED AS AN ONE-STEP PROCESS FOR THE BIOLOGICAL REDUCTION OF NITRATES TO MOLAR NITROGEN. A SIMPLE DENITRIFICATION MODEL WAS DEVELOPED THAT WAS USED FOR THE OPTIMIZATION OF A CSTR REACTOR UNDER STEADY STATE OPERATING CONDITIONS, OR UNDER CONDITIONS OF PULSED PERIODIC ALTERNATION OF AEROBIC /ANOXIC CONDITIONS.Η ΑΠΟΝΙΤΡΟΠΟΙΗΣΗ ΕΙΝΑΙ ΜΙΑ ΒΙΟΛΟΓΙΚΗ ΔΙΕΡΓΑΣΙΑ ΠΟΥ ΣΤΟΧΕΥΕΙ ΣΤΗΝ ΑΠΟΜΑΚΡΥΝΣΗ ΤΟΥ ΑΖΩΤΟΥ ΣΤΗ ΜΟΡΦΗ ΤΩΝ ΝΙΤΡΙΚΩΝ Η/ΚΑΙ ΝΙΤΡΩΔΩΝ ΑΠΟ ΤΟ ΝΕΡΟ, ΕΙΤΕ ΠΡΟΚΕΙΤΑΙ ΓΙΑ ΠΟΣΙΜΟ ΝΕΡΟ, ΕΙΤΕ ΓΙΑ ΑΣΤΙΚΑ ΛΥΜΑΤΑ ΚΑΙ ΒΙΟΜΗΧΑΝΙΚΑ ΥΓΡΑ ΑΠΟΒΛΗΤΑ. Η ΔΙΕΡΓΑΣΙΑ ΑΥΤΗ ΠΡΑΓΜΑΤΟΠΟΙΕΙΤΑΙ ΑΠΟ ΕΤΕΡΟΤΡΟΦΑ, ΠΡΟΑΙΡΕΤΙΚΑ ΑΕΡΟΒΙΑ ΒΑΚΤΗΡΙΑ ΚΑΤΩ ΑΠΟ ΑΝΟΞΙΚΕΣ ΣΥΝΘΗΚΕΣ. ΓΙΑ ΤΟ ΣΧΕΔΙΑΣΜΟ ΜΙΑΣ ΜΟΝΑΔΑΣ ΑΠΟΝΙΤΡΟΠΟΙΗΣΗΣ ΑΠΑΙΤΕΙΤΑΙ Η ΥΠΑΡΞΗ ΕΝΟΣ ΚΙΝΗΤΙΚΟΥ ΜΟΝΤΕΛΟΥ ΠΡΟΣΟΜΟΙΩΣΗΣ ΤΗΣ ΔΙΕΡΓΑΣΙΑΣ, ΙΚΑΝΟΥ ΝΑ ΠΕΡΙΓΡΑΦΕΙ ΜΕ ΙΚΑΝΟΠΟΙΗΤΙΚΗ ΑΚΡΙΒΕΙΑ ΤΟΝ ΡΥΘΜΟ ΜΙΚΡΟΒΙΑΚΗΣ ΑΝΑΠΤΥΞΗΣ ΚΑΙ ΑΠΟΝΙΤΡΟΠΟΙΗΣΗΣ ΚΑΤΩ ΑΠΟ ΑΕΡΟΒΙΕΣ, ΑΝΟΞΙΚΕΣ ΚΑΙ ΜΕΤΑΒΑΤΙΚΕΣ ΣΥΝΘΗΚΕΣ ΑΝΑΠΤΥΞΗΣ. ΓΙΑ ΤΟ ΣΚΟΠΟ ΑΥΤΟ, ΠΡΑΓΜΑΤΟΠΟΙΗΘΗΚΑΝ ΠΕΙΡΑΜΑΤΑ ΣΕ ΑΝΤΙΔΡΑΣΤΗΡΑ ΔΙΑΛΕΙΠΟΝΤΟΣ ΕΡΓΟΥ ΜΕ ΚΑΘΑΡΗ ΚΑΛΛΙΕΡΓΕΙΑ ΕΝΟΣ ΑΝΤΙΠΡΟΣΩΠΕΥΤΙΚΟΥ ΑΠΟΝΙΤΡΟΠΟΙΗΤΙΚΟΥ ΜΙΚΡΟΟΡΓΑΝΙΣΜΟΥ (PSEUDOMONAS DENITRIFICANS) ΣΕ ΣΥΝΘΕΤΙΚΟ ΘΡΕΠΤΙΚΟ ΜΕΣΟ. ΘΕΩΡΩΝΤΑΣ ΤΗΝ ΑΠΟΝΙΤΡΟΠΟΙΗΣΗ ΩΣ ΔΙΕΡΓΑΣΙΑ ΑΝΑΓΩΓΗΣ ΤΩΝ ΝΙΤΡΙΚΩΝ ΠΡΟΣ ΑΕΡΙΟ ΑΖΩΤΟ ΣΕ ΔΥΟ ΣΤΑΔΙΑ(ΕΝΔΙΑΜΕΣΗ ΠΑΡΑΓΩΓΗ ΝΙΤΡΩΔΩΝ), ΑΝΑΠΤΥΧΘΗΚΕ ΕΝΑ ΑΞΙΟΠΙΣΤΟ ΚΙΝΗΤΙΚΟ ΜΟΝΤΕΛΟ ΠΕΡΙΓΡΑΦΗΣ ΤΗΣ ΔΙΕΡΓΑΣΙΑΣ, ΤΟ ΟΠΟΙΟ ΧΡΗΣΙΜΟΠΟΙΗΘΗΚΕ ΓΙΑ ΤΟ ΒΕΛΤΙΣΤΟ ΣΧΕΔΙΑΣΜΟ ΔΙΕΡΓΑΣΙΩΝ ΑΠΟΝΙΤΡΟΠΟΙΗΣΗΣ ΣΕ ΑΝΤΙΔΡΑΣΤΗΡΕΣ ΤΥΠΟΥ CSTR ΚΑΙ SBR (SEQUENCING BATCH REACTOR). Η ΘΕΩΡΗΣΗ ΤΗΣ ΑΠΟΝΙΤΡΟΠΟΙΗΣΗΣ ΩΣ ΔΙΕΡΓΑΣΙΑΣ ΕΝΟΣ ΣΤΑΔΙΟΥ ΑΝΑΓΩΓΗΣ ΤΩΝ ΝΙΤΡΙΚΩΝ, ΟΔΗΓΗΣΕ ΕΠΙΠΛΕΟΝ ΣΤΗΝ ΑΝΑΠΤΥΞΗ ΕΝΟΣ ΑΠΛΟΥ ΚΑΙ ΕΥΧΡΗΣΤΟΥ ΜΑΘΗΜΑΤΙΚΟΥ ΜΟΝΤΕΛΟΥ. ΤΟ ΜΟΝΤΕΛΟ ΑΥΤΟ ΧΡΗΣΙΜΟΠΟΙΗΘΗΚΕ ΓΙΑ ΤΗ ΔΙΕΡΕΥΝΗΣΗ, ΜΕ ΧΡΗΣΗ ΤΕΧΝΙΚΩΝ ΒΕΛΤΙΣΤΟΥ ΕΛΕΓΧΟΥ, ΤΗΣ ΠΙΘΑΝΟΤΗΤΑΣ ΒΕΛΤΙΣΤΟΠΟΙΗΣΗΣ ΤΗΣ ΔΙΕΡΓΑΣΙΑΣ ΣΕ ΑΝΤΙΔΡΑΣΤΗΡΑ ΤΥΠΟΥ CSTR

Effect of pH on growth and lipid accumulation kinetics of the microalga Chlorella vulgaris grown heterotrophically under sulfur limitation

A

Vermi-Conversion of Anaerobic Sludges by <i>Eisenia fetida</i> Earthworms

Sludge management is considered a difficult and challenging task and is a priority of environmental policy. This study evaluates the transformation of the anaerobic sludge of agroindustrial wastes (cow manure, anaerobic sludge mixtures) directly to compost using Eisenia fetida earthworms (vermicomposting) in relation to sludge quality; moreover, it investigates the effects of different sludge compositions on vermicompost physicochemical properties. In particular, the biostabilization of anaerobic sludge (AS1) produced in excess from the wastewater treatment plant (WWTP) of Patras, Greece, and mixed anaerobic sludge (AS2) originating from the effluents of a laboratory anaerobic co-digestion system treating an agroindustrial waste mixture (olive mill wastewater, cheese whey, and liquid cow manure in a ratio of 55: 40: 5 (w/w), respectively) mixed with cow dung (CD) using Eisenia fetida earthworms was examined. Comparing the mixtures of CD-AS1 to CD-AS2, superior results were obtained with the use of AS2 since an increase in N-P-K was observed when either 10% (22%, 51.8%, and 2.4%, respectively) or 15% of AS2 (38.7%, 14.1%, and 8.1% respectively) was used. Although a reduction in earthworms’ growth was observed compared to 100% CD, during the vermicomposting of the CD-AS mixtures, 410 and 250 mg/earthworm was sustained in the mixtures of 85% CD-15% AS2 and 80% CD-20% AS2 after a period of 63 and 70 days of vermicomposting, respectively

Thermophilic Dark Fermentation of Olive Mill Wastewater in Batch Reactors: Effect of pH and Organic Loading

In recent decades, olive oil consumption has almost tripled worldwide. Olive oil production is linked with the production of enormous amounts of olive mill wastewater, the main by-product derived from three-phase olive mills. Due to the environmental risks of olive mill wastewater disposal, the management and valorization of the specific waste stream is of great importance. This work focuses on the thermophilic dark fermentation of olive mill wastewater in batch reactors, targeting pH optimization and the organic loading effect. A series of experiments were performed, during which the organic load of the substrate remained at 40 g/L after dilution with tap water, and the pH was tested in the range of 4.5 to 7.5. The maximum yield in terms of produced hydrogen was obtained at pH 6.0, and the yields were 0.7 mol H2/mol glucose or 0.5 L H2/Lreactor. At the same conditions, a reduction of 62% of the waste’s phenols was achieved. However, concerning the effect of organic loading at the optimized pH value (6.0), a further increase in the organic load minimized the hydrogen production, and the overall process was strongly inhibited