Maria Alexandri

Evaluation of by-products from the biodiesel industry as fermentation feedstock for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production by Cupriavidus necator

Utilization of by-products from oilseed-based biodiesel production (crude glycerol, rapeseed meal hydrolysates) for microbial polyhydroxyalkanoate (PHA) production could lead to the replacement of expensive carbon sources, nutrient supplements and precursors for co-polymer production. Batch fermentations in shake flasks with varying amounts of free amino nitrogen led to the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) with a 2.8-8% 3HV content. Fed-batch fermentations in shake flasks led to the production of 10.9g/L P(3HB-co-3HV) and a 55.6% P(3HB-co-3HV) content. NaCl concentrations between 2 and 6g/L gradually became inhibitory to bacterial growth and PHA formation, whereas in the case of K(2)SO(4), the inhibitory effect was observed only at concentrations higher than 20g/L. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and nuclear magnetic resonance ((13)C NMR) demonstrated that the incorporation of 3HV into the obtained P(3HB-co-3HV) lowered glass transition temperature, crystallinity and melting point as compared to polyhydroxybutyrate. Integrating PHA production in existing oilseed-based biodiesel plants could enhance the viability and sustainability of this first generation biorefinery.

Evaluation of an integrated biorefinery based on fractionation of spent sulphite liquor for the production of an antioxidant-rich extract, lignosulphonates and succinic acid

Spent sulphite liquor (SSL) has been used for the production of lignosulphonates (LS), antioxidants and bio-based succinic acid. Solvent extraction of SSL with isopropanol led to the separation of approximately 80% of the total LS content, whereas the fermentations carried out using the pretreated SSL with isopropanol led to the production of around 19g/L of succinic acid by both Actinobacillus succinogenes and Basfia succiniciproducens. Fractionation of SSL via nanofiltration to separate the LS and solvent extraction using ethyl acetate to separate the phenolic compounds produced a detoxified sugar-rich stream that led to the production of 39g/L of succinic acid by B. succiniciproducens. This fractionation scheme resulted also in the production of 32.4g LS and 1.15g phenolic-rich extract per 100g of SSL. Both pretreatment schemes removed significant quantities of metals and heavy metals. This novel biorefinery concept could be integrated in acidic sulphite pulping mills.

Succinic acid production by immobilized cultures using spent sulphite liquor as fermentation medium

Spent sulphite liquor (SSL) was used as carbon source for the production of succinic acid using immobilized cultures of Actinobacillus succinogenes and Basfia succiniciproducens on two different supports, delignified cellulosic material (DCM) and alginate beads. Fed-batch immobilized cultures with A. succinogenes in alginates resulted in higher sugar to succinic acid conversion yield (0.81g/g) than the respective yield achieved (0.65g/g) when DCM immobilized cultures were used. The final succinic acid concentration and yield achieved in fed-batch with immobilized cultures of B. succiniciproducens in alginates (45g/L and 0.66g/g) were higher than A. succinogenes immobilized cultures (35.4g/L and 0.61g/g) using nano-filtrated SSL as fermentation medium. Immobilized cultures of B. succiniciproducens in alginate beads were reused in four sequential fed-batch fermentations of nano-filtrated SSL leading to the production of 64.7g of succinic acid with a yield range of 0.42-0.67g/g and productivity range of 0.29-0.65g/L/h. The immobilized cultures improved the efficiency of succinic acid production as compared to free cell cultures.