Polyhydroxyalkanoates: Characteristics, production, recent developments and applications

Spent coffee ground (SCG) contains large amounts of organic compounds (i.e. fatty acids, amino acids, polyphenols, minerals and polysaccharides) that justify its valorization. Earlier innovation explored the extraction of specific components such as oil, flavor, terpenes, and alcohols as value-added products. However, by-products of coffee fruit and bean processing can also be considered as potential functional ingredients for the food industry. There is an urgent need for practical and innovative ideas to use this low cost SCG and exploit its full potential increasing the overall sustainability of the coffee agro-industry.

Spent coffee grounds: A review on current research and future prospects

Exploitation of Food Industry Waste for High-Value Products.

Producing microbial polyhydroxyalkanoate (PHA) biopolyesters in a sustainable manner

Production of bioplastic through food waste valorization.

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.

Libor Eremka

Papers

Utilization of oil extracted from spent coffee grounds for sustainable production of polyhydroxyalkanoates.