Rapid estimation of kinetic parameters for thermal decomposition of penicillins by modulated thermogravimetric analysis.

Modulated thermogravimetic analysis (MTGA) is evaluated for the rapid estimation of thermal stability using several penicillin antibiotics as model compounds. The MTGA technique utilizes an oscillatory temperature program to obtain Arrhenius kinetic parameters through a mass loss during thermal degradation. To evaluate the reliability of this technique, activation energies (E(a)), log pre-exponential factor (logZ), and log first order rate constants (logk) obtained by MTGA for the thermal decomposition of ampicillin anhydrous, ampicillin trihydrate, ampicillin sodium salt, and penicillin G potassium salt are compared to existing literature values. The logk values estimated by MTGA agreed well with literature values when the weight loss observed by MTGA was shown to be due to the first decomposition step of the compound. The E(a) and logZ values determined by MTGA did not consistently agree with literature values as these parameters increased with decreasing heating rate (beta). The increase in E(a) and logZ values with decreasing beta seemed to offset each other to some extent to yield a relatively consistent logk estimate regardless of beta.

Microbial utilization of aqueous co-products from hydrothermal liquefaction of microalgae Nannochloropsis oculata.

Hydrothermal liquefaction of algae biomass is a promising technology for the production of sustainable biofuels, but the non-oil, aqueous co-product of the process has only been examined to a limited extent. The aqueous phase from liquefaction of the alga Nannochloropsis oculata (AqAl) was used to make growth media for model heterotrophic microorganisms Escherichia coli, Pseudomonas putida, and Saccharomyces cerevisiae. Growth rates, yields, and carbon/nitrogen/phosphorus uptake were measured. E. coli and P. putida could grow using AqAl as the sole C, N, and P source in media containing 10 vol.%-40 vol.% AqAl with the best growth occurring at 20 vol.%. S. cerevisiae could grow under these conditions only if the media were supplemented with glucose. The results indicate that in a biorefinery utilizing algae liquefaction, the aqueous co-product may be recycled via microbial cultures with significantly less dilution than previously published methods.