Conversion of Short and Medium Chain Fatty Acids into Novel Polyhydroxyalkanoates Copolymers by Aeromonas sp. AC_01.

Polyhydroxyalkanoates (PHAs) production by Aeromonas sp. AC_01 was investigated using synthetic and waste derived short and medium chain fatty acids (SMCFAs). The obtained results revealed that the analyzed bacterial strain was able to grow and synthesize PHAs using SMCFAs. The highest PHA productivity was observed in the cultivation supplemented with a mixture of acetic acid and butyric acid (3.89 mg/L·h). Furthermore, SMCFAs-rich stream, derived from acidogenic mixed culture fermentation of acid whey, was found to be less beneficial for PHA productivity than its synthetic mixture, however the PHA production was favored by the nitrogen-limited condition. Importantly, Aeromonas sp. AC_01 was capable of synthesizing novel scl-mcl copolymers of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), 3-hydroxytridecanoate (3HtriD) and/or 3-hydroxytetradecaonate (3HTD) with high 3HB and 3HV fractions. They were identified with alterable monomers composition depending on the culture conditions used. Moreover, in-depth thermal analyses proved that they are highly resistant to thermal degradation regardless of their monomeric composition. The obtained results confirm that Aeromonas sp. AC_01 is a promising candidate for the biotechnological production of PHAs from SMCFAs with thermal properties that can be tuned together with their chemical composition by the corresponding adjustment of the cultivation process.

Treatment of different parts of corn stover for high yield and lower polydispersity lignin extraction with high-boiling alkaline solvent.

The influence of different parts of corn stover on lignin extraction was investigated. Five kinds of lignin were isolated by the high boiling point solvent extraction from the whole corn stover and four different parts including leaf, husk, bark and pith. The optimal condition was obtained: 6.25 g/L NaOH, 140 °C, 1 h and 60% (v/v) 1,4-butanediol. The extracted lignins were then characterized. FT-IR analysis revealed that all of the lignins were typically herbaceous. The lignin extracted from husk contained more S unit. Gel permeation chromatography analysis showed that it was necessary to separate corn stover into different parts to obtain low polydispersity lignin. The SEM and FT-IR analysis proved that the lignin dissolution was related to the tightness structure presenting a positive correlation with hydrogen bond index.