Screening of commercial enzymes for poly(ethylene terephthalate) (PET) hydrolysis and synergy studies on different substrate sources.

Poly(ethylene terephthalate) (PET) is one of the most consumed plastics in the world. The development of efficient technologies for its depolymerization for monomers reuse is highly encouraged, since current recycling rates are still very low. In this study, 16 commercial lipases and cutinases were evaluated for their abilities to catalyze the hydrolysis of two PET samples. Humicola insolens cutinase showed the best performance and was then used in reactions on other PET sources, solely or in combination with the efficient mono(hydroxyethyl terephthalate)-converting lipase from Candida antarctica. Synergy degrees of the final titers of up to 2.2 (i.e., more than double of the concentration when both enzymes were used, as compared to their use alone) were found, with increased terephthalic acid formation rates, reaching a maximum of 59,989 µmol/L (9.36 g/L). These findings open up new possibilities for the conversion of post-consumer PET packages into their minimal monomers, which can be used as drop in at existing industrial facilities.

Seasonal variation of the organic and inorganic composition of sugarcane vinasse: main implications for its environmental uses.

Sugarcane vinasse is the main waste stream of the Brazilian agroindustry. The typical composition of sugarcane vinasse gives it a high polluting potential that implies the necessity to define sustainable strategies for managing this waste. Knowledge of the inorganic and organic composition of vinasse and its seasonal variation is extremely important to conduct scientific research to define alternative managements for vinasse disposal other than fertigation. This study evaluated the variability of vinasse composition throughout the same harvesting season and among three harvesting seasons of one Brazilian annexed biorefinery (2015-2017). The contents of chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total solids (TS), suspended solids (SS), salinity (K+, Na+, Ca2+, Mg2+, Cl-, F-), nutrients (N, P, S), trace metals (Al3+, As2+, Ba2+, Cd2+, Cr3+, Co2+, Cu2+, Fe2+, Pb2+, Mn2+, Hg2+, Mo2+, Ni2+, Se2+, Zn2+), and specific soluble organic compounds (sugars, alcohols, and organic acids), as well as pH and conductivity, were monitored in 13 samples. The results indicated that sugarcane vinasse is a suitable feedstock for biological treatments, such as anaerobic digestion processes for energy recovery, as well as substrate for biomass (e.g., microalgae, energy crops, lignocellulosic biomass) growth. The application of a previous treatment makes vinasse a more environmentally friendly natural fertilizer for land fertigation.