Sustainable biofuels, biomaterials, and fine chemicals production is a critical matter that research teams around the globe are focusing on nowadays. Polyhydroxyalkanoates represent one of the biomaterials of the future due to their physicochemical properties, biodegradability, and biocompatibility. Designing efficient and economic bioprocesses, combined with the respective social and environmental benefits, has brought together scientists from different backgrounds highlighting the multidisciplinary character of such a venture. In the current review, challenges and opportunities regarding polyhydroxyalkanoate production are presented and discussed, covering key steps of their overall production process by applying pure and mixed culture biotechnology, from raw bioprocess development to downstream processing.

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The aim of the present study was to investigate the potential of hydrogen and subsequent methane production from raw cheese whey at 35 °C. The fermentative hydrogen production process from raw cheese whey was conducted in a continuous-type stirred tank bioreactor, operated at low hydraulic retention time (HRT; 24 h). In this stage, the carbohydrates contained in cheese whey are fermented to a mixture of acids and a gaseous mixture rich in hydrogen. The continuous fermentative hydrogen production was sustained by the indigenous microflora already contained in the raw cheese whey because the bioreactor was not seeded with any source of inoculum. At a HRT of 24 h, the hydrogen production rate was 7.53 L of H 2 /day, while the yield of hydrogen produced was 0.041 m 3 of H 2 /kg of chemical oxygen demand (COD) added or 2.49 L of H 2 /L of cheese whey. The mixed liquor from this stage was further digested to biogas in a periodic anaerobic baffled reactor (PABR), a baffled-type bioreactor. The PABR was operated at HRTs of 20, 10, and 4.4 days. The highest biogas and methane production rates were 105.9 L of biogas/day and 75.6 L of CH 4 /day, respectively, and were obtained at an HRT of 4.4 days. During this stage, COD reduction reached 94%, obtained at an HRT of 4.4 days. Furthermore, the methane potential of the raw cheese whey was assessed by conducting a biochemical methane potential test. It was estimated to be 0.31 m 3 of CH 4 /kg of COD added or 17.9 L of CH 4 /L of cheese whey. This work demonstrated that biohydrogen production from cheese whey can be very efficiently coupled with methane production in a subsequent step, exploiting the gaseous biofuel potential of this wastewater type.

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Changing waste management practice, introduction of new technologies, and population demographics and behaviour will impact on both quantity and composition of future waste streams. Laboratory-scale anaerobic digestion of the mechanically-separated organic fraction of municipal solid waste (ms-OFMSW) was carried out at relatively low organic loading rates (OLR), and results analysed using an energy modelling tool. Thermophilic operation with water addition and liquor recycle was compared to co-digestion with dilution water replaced by sewage sludge digestate (SSD); thermophilic and mesophilic mono-digestion were also tested at low OLR. All thermophilic conditions showed stable operation, with specific methane production (SMP) from 0.203-0.296 m 3 CH4 kg -1 volatile solids (VS). SSD addition increased biogas production by ~20% and there was evidence of further hydrolysis and degradation of the SSD. Long-term operation at 1 kg VS m -3 day -1 had no adverse effect except in mesophilic conditions where SMP was lower at 0.256 m 3 CH4 kg -1 VS and stability was reduced, especially during OLR increases. This was probably due to low total ammonia nitrogen, which stabilised at ~0.2 g N kg -1 and limited the buffering capacity. Energy analysis showed thermophilic operation at OLR 2 g VS L -1 day -1 gave 42% of the theoretical methane potential and 38% of the higher heating value, reducing to 37% and 34% respectively in mesophilic conditions. Scenario modelling indicated that under low ms-OFMSW load even an energy-depleted co-substrate such as SSD could contribute to the energy balance, and would be a better diluent than water due to its nutrient and buffering capacity.

Αμυντικές Δράσεις εν καιρώ ειρήνης» που πραγματοποιήθηκε στην Πάτρα από την Μονάδα Ρύπανσης-Διαχείρισης Περιβάλλοντος και Οικοτοξικολογίας του Τμήματος Βιολογίας. 2004 (27/05/2004-30/05/2004): Συμμετοχή και παρουσίαση (poster) στο 26 ο Πανελλήνιο Συνέδριο Βιολογίας που πραγματοποιήθηκε στον Βόλο από την Ελληνική Εταιρεία Βιολογικών Επιστημών. 2003 (19/02/2003): Συμμετοχή στην Ημερίδα «FORUM ΝΕΩΝ ΕΠΙΣΤΗΜΟΝΩΝ, Εφαρμοσμένη Έρευνα στο χώρο των Εντατικών και Εκτατικών Υδατοκαλλιεργειών» που πραγματοποιήθηκε στο Συνεδριακό Κέντρο του Πανεπιστημίου Πατρών από το Τμήμα Βιολογίας, το ΙΧΘΥΚΑ Α.Ε. και την Υπηρεσία Διαχείρισης Επιχειρησιακού Προγράμματος "Αλιεία" του Υπουργείου Γεωργίας.