Enhanced fermentative hydrogen production from potato waste by enzymatic pretreatment

Biological pretreatment and enzymatic hydrolysis have a potential role in the economic production of sugars and fuels from starch biomass. In this study, the Inoculum/Substrate (I/S) ratio effect and enzymatic pretreatments of potato peels for biohydrogen production in batch reactors were investigated. Two enzymes, α-Amylase and Cellulase, were tested separately and coexistent. Results showed that enzymatic hydrolysis using α-Amylase in mesophilic conditions enhanced carbohydrate concentration from 24.10 g/L to 53.47 g/L, whereas, the use of Cellulase and equi-volumetric mixture of both tested enzymes resulted in 47.16 and 48.16 g/L, respectively. The maximum biohydrogen cumulative production of 263 mL (equivalent to 430.37 mL H2/gVSadded) was obtained using the optimum I/S ratio of 1/6 gVS/gVS at pH 5.5 and incubation temperature of 55°C after 20 days of dark fermentation of potato waste without enzymatic treatment. Under the same operating conditions of the I/S ratio, pH, temperature and the best enzymatic treatment (3 h of substrate enzymatic hydrolysis by α-Amylase), the maximum yield of biohydrogen was 1088 mL (1780.39 mL H2/gVSadded). The enzymatic hydrolysis method adopted in this study can make overall biohydrogen production an effective process. The modified Gompertz model was found to be an adequate fit for biohydrogen production.

Stability and Biotransformation of 6:2 Fluorotelomer Sulfonic Acid, Sulfonamide Amine Oxide, and Sulfonamide Alkylbetaine in Aerobic Sludge

The 6:2 fluorotelomer sulfonamide (6:2 FTSAm)-based compounds signify a prominent group of per- and polyfluoroalkyl substances (PFAS) widely used in contemporary aqueous film-forming foam (AFFF) formulations. Despite their widespread presence, the biotransformation behavior of these compounds in wastewater treatment plants remains uncertain. This study investigated the biotransformation of 6:2 FTSAm-based amine oxide (6:2 FTNO), alkylbetaine (6:2 FTAB), and 6:2 fluorotelomer sulfonic acid (6:2 FTSA) in aerobic sludge over a 100-day incubation period. The biotransformation of 6:2 fluorotelomer sulfonamide alkylamine (6:2 FTAA), a primary intermediate product of 6:2 FTNO, was indirectly assessed. Their stability was ranked based on the estimated half-lives (t1/2): 6:2 FTAB (no obvious products were detected) ≫ 6:2 FTSA (t1/2 ≈28.8 days) > 6:2 FTAA (t1/2 ≈11.5 days) > 6:2 FTNO (t1/2 ≈1.2 days). Seven transformation products of 6:2 FTSA and 15 products of 6:2 FTNO were identified through nontarget and suspect screening using high-resolution mass spectrometry. The transformation pathways of 6:2 FTNO and 6:2 FTSA in aerobic sludge were proposed. Interestingly, 6:2 FTSAm was hardly hydrolyzed to 6:2 FTSA and further biotransformed to perfluoroalkyl carboxylic acids (PFCAs). Furthermore, the novel pathways for the generation of perfluoroheptanoic acid (PFHpA) from 6:2 FTSA were revealed.