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Waste rapeseed oil is a useful substrate for polyhydroxyalkanoates (PHA) production employing Cupriavidus necator H16. In fed-batch mode, we obtained biomass and PHA yields of 138 and 105 g l -1 , respectively. Yield coefficient and volumetric productivity were 0.83 g PHA per g oil and 1.46 g l -1 h -1 , respectively. Propanol at 1% (v/v) enhanced both PHA and biomass formation significantly and, furthermore, resulted in incorporation of 3-hydroxyvalerate units into PHA structure. Thus, propanol can be used as an effective precursor of 3-hydroxyvalarete for production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer. During the fed-batch cultivation, propanol concentration was maintained at 1% which resulted in 8% content of 3-hydroxyvalerate in copolymer.

Polyhydroxyalkanoates (PHAs) are very promising materials that might serve as an environmentally friendly alternative to petrochemical plastics. The main obstacle preventing PHAs from entering the market massively is the final cost of the polymer material, a significant portion of which is attributed to carbon substrate. Hence, the researchers have been intensively seeking cheap substrates for sustainable production of PHAs. Lignocellulose represents a very promising substrate for PHAs production -it is abundant, cheap, and it does not compete with human food chain. On the other hand, utilization of lignocellulose materials as substrates for biotechnological processes represents a challenge due to many factors, such as necessary hydrolysis of the biomass to yield fermentable sugars and presence of numerous antimicrobial agents. Therefore, this work summarizes recent advances in biotechnological conversion of lignocellulose materials into PHAs. The review not only deals with the process of fermentation, but it also considers different approaches of lignocellulose hydrolysis and detoxification.

Spent coffee grounds (SCG), an important waste product of the coffee industry, contain approximately 15 wt% of coffee oil. The aim of this work was to investigate the utilization of oil extracted from SCG as a substrate for the production of poly(3-hydroxybutyrate) (PHB) by Cupriavidus necator H16. When compared to other waste/inexpensive oils, the utilization of coffee oil resulted in the highest biomass as well as PHB yields. Since the correlation of PHB yields and the acid value of oil indicated a positive effect of the presence of free fatty acids in oil on PHB production (correlation coefficient R (2) = 0.9058), superior properties of coffee oil can be probably attributed to the high content of free fatty acids which can be simply utilized by the bacteria culture. Employing the fed-batch mode of cultivation, the PHB yields, the PHB content in biomass, the volumetric productivity, and the Y P/S yield coefficient reached 49.4 g/l, 89.1 wt%, 1.33 g/(l h), and 0.82 g per g of oil, respectively. SCG are annually produced worldwide in extensive amounts and are disposed as solid waste. Hence, the utilization of coffee oil extracted from SCG is likely to improve significantly the economic aspects of PHB production. Moreover, since oil extraction decreased the calorific value of SCG by only about 9 % (from 19.61 to 17.86 MJ/kg), residual SCG after oil extraction can be used as fuel to at least partially cover heat and energy demands of fermentation, which should even improve the economic feasibility of the process.

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