Pectin is widely used in the food and pharmaceutical industries. However, data on sweet potato pectin extraction and structural property analyses are lacking. Here, for the high-value utilization of agricultural processing waste, sweet potato residue, a byproduct of sweet potato starch processing, was used as raw material. Ammonium oxalate, trisodium citrate, disodium hydrogen phosphate, hydrochloric acid and citric acid were used as extractants for the pectin constituents, among which ammonium oxalate had a high extraction rate of sweet potato pectin, low ash content and high molecular weight. Structural and gelation analyses were conducted on ammonium oxalate-extracted purified sweet potato pectin (AMOP). Analyses showed that AMOP is a rhamnogalacturonan-I-type pectin, with a molecular weight of 192.5 kg/mol. Chemical titration and infrared spectroscopy analysis confirmed that AMOP is a low-ester pectin, and scanning electron and atomic force microscopy demonstrated its linear molecular structure. Gelation studies have revealed that Ca²⁺ is the key factor for gel formation, and that sucrose significantly enhanced gel hardness. The highest AMOP gel hardness was observed at pH 4, with a Ca²⁺ concentration of 30 mg/g, pectin concentration of 2%, and sucrose concentration of 40%, reaching 128.87 g. These results provide a foundation for sweet potato pectin production and applications.

Cardiovascular disease (CVD) has become the leading cause of death, and it is critical to develop new functional foods to prevent intravascular thrombosis, the key cause of CVD. Fermented soy-based food is a good choice because of its native fibrinolytic enzyme (FE) activity. In this study, a strain that can produce a new type of fibrinolytic enzyme was selected from Chinese Douchi and identified as Bacillus licheniformis SFD-Y5 by molecular biology experiments and physiological and biochemical experiments. Single factor experiments combined with statistical experiments, including Plackett–Burman experiment, steepest ascent experiment and RSM (Box–Behnken design), were used to optimize the fermentation of FE by B. licheniformis SFD-Y5. The final FE activity was 2434.45 ± 28.49 IU/mL under optimal conditions, which is the highest FE activity produced by wild B. licheniformis so far. Further studies showed that Y5 FE is a serine metalloproteinase with good stability at alkaline pHs (pH 8.0–11.0). The results of our study could lay a foundation for the future production, molecular modification and further application in functional foods of Y5 FE.

Starch production from fresh sweet potatoes generates process wastewater called sweet potato cell liquid (SPCL), which is rich in sweet potato protein (SPP). Currently, the commonly used protein recovery methods, such as isoelectric point precipitation and ultrafiltration, were not suitable for...

Acetoin (AC) is an important platform compound with two enantiomers (R)-AC and (S)-AC. Due to its unique spatial structure, optically pure AC has particularly high application in asymmetric synthesis. Highly optically pure AC could be produced from glucose using biofermentation technology. In this paper, we have observed that the recovered AC product from the fermentation broth containing (R)-AC was a racemic mixture. The changes of the enantiomeric excess (e.e.) of (R)-AC enantiomers in the feed solution during the recovery process were then investigated, confirming that the racemization occurs during solvent distillation. Further studies showed that high temperature is the main factor affecting the conversion of the two enantiomers, while low temperature significantly prevents this conversion reaction. Therefore, we optimized the solvent recovery process and used vacuum distillation to reduce the distillation process temperature, which effectively prevented the racemization: obtains AC products with more than 98% purity and successfully maintained the proportion of (R)-AC above 96%. To our knowledge, this is the first report on the factors affecting the enantiomeric purity in the downstream extraction process of AC production by fermentation.