Sustainability Evaluation of Polyhydroxyalkanoate Production from Slaughterhouse Residues Utilising Emergy Accounting

Enhanced docosahexaenoic acid production from cane molasses by engineered and adaptively evolved Schizochytrium sp

Cane molasses (CM) is a sugar-rich agro-industrial byproduct. The purpose of this study is to synthesize docosahexaenoic acid (DHA) in Schizochytrium sp. by using CM. The single factor analysis showed that sucrose utilization was the main factor limiting the utilization of CM. Therefore, the endogenous sucrose hydrolase (SH) was overexpressed in Schizochytrium sp., which enhanced the sucrose utilization rate 2.57-fold compared to the wild type. Furthermore, adaptive laboratory evolution was used to further improve sucrose utilization from CM. Comparative proteomics and RT-qPCR were used out to analyze the metabolic differences of evolved strain grown on CM and glucose, respectively. Finally, a constant flow rate CM feeding strategy was implemented, whereby the DHA titer and lipid yield of the final strain OSH-end reached 25.26 g/L and 0.229 g/g sugar, respectively. This study demonstrated the CM is a cost-effective carbon source for industrial DHA fermentation.

Environmental Evaluation of Polyhydroxyalkanoates from Animal Slaughtering Waste Using Material Input Per Service Unit

The massive production and extensive use of fossil-based non-biodegradable plastics are leading to their environmental accumulation and ultimately cause health threats to animals, humans, and the biosphere in general. The problem can be overcome by developing eco-friendly ways for producing plastics-like biopolymers from waste residues such as of agricultural origin. This will solve two currently prevailing social issues: waste management and the efficient production of a biopolymer that is environmentally benign, polyhydroxyalkanoates (PHA). The current study assesses the environmental impact of biopolymer (PHA) manufacturing, starting from slaughterhouse waste as raw material. The Material Input Per Service Unit methodology (MIPS) is used to examine the sustainability of the PHA production process. In addition, the impact of shifting from business-as-usual energy provision (i.e., electricity from distribution grid network and heat provision from natural gas) to alternative renewable energy sources is also evaluated. As a major outcome, it is shown that the abiotic material contribution for PHA production process is almost double for using hard coal as an energy source than the petro-plastic low-density-poly(ethene) (LPDE), which PHA shall ultimately replace. Likewise, abiotic material contribution is 43% and 7% higher when using the electricity from the European electricity mix (EU-27 mix) and biogas, respectively, than in the case of LDPE production. However, PHA production based on wind power for energy provision has 12% lower abiotic material input than LDPE. Furthermore, the water input decreases when moving from the EU-27 mix to wind power. The reduction in water consumption for various electricity provision resources amounts to 20% for the EU-27 mix, 25% for hard coal, 71% for wind, and 70% for biogas. As the main conclusion, it is demonstrated that using wind farm electricity to generate PHA is the most environmentally friendly choice. Biogas is the second-best choice, although it requires additional abiotic material input.