In this study, effects of different pretreatment methods on the enzymatic digestibility of Pennisetum alopecuroides, a ubiquitous wild grass in China, were investigated to evaluate its potential as a feedstock for biofuel production. The stalk samples were separately pretreated with H2SO4, NaOH and FeCl3 solutions of different concentrations at 120 °C for 30 min, after which enzymatic hydrolysis was conducted to measure the digestibility of pretreated samples. Results demonstrated that different pretreatments were effective at removing hemicellulose, among which ferric chloride pretreatment (FCP) gave the highest soluble sugar recovery (200.2 mg/g raw stalk) from the pretreatment stage. In comparison with FCP and dilute acid pretreatment (DAP), dilute alkaline pretreatment (DALP) induced much higher delignification and stronger morphological changes of the biomass, making it more accessible to hydrolysis enzymes. As a result, DALP using 1.2% NaOH showed the highest total soluble sugar yield through the whole process from pretreatment to enzymatic hydrolysis (508.5 mg/g raw stalk). The present work indicates that DALP and FCP have the potential to enhance the effective bioconversion of lignocellulosic biomass like P. alopecuroides, hence making this material a valuable and promising energy plant.
Green-kernel black bean (Vigna cylindrica (L.) Skeels) were processed with various treatments including soaking, roasting, cooking, autoclave and germination. The effects of these treatments on the chemical compostion, mineral, anti-nutrients, antioxidant and physical properties of the resultant flours were analyzed. The results indicate that green-kernel black bean was excellent sources of dietary fiber (165.4 g/kg), magnesium (2190 mg/kg), anthocyanin (791.6 mg/kg) and phenolic compounds (4.4 g gallic acid equivalent/kg), which were virtually higher than those reported for other pulses. Among the studied processing methods, cooking and autoclave provided the most evident effects on all flour characteristics, where the water holing capacity was enhanced and the flour became brighter. In addition, the levels of anti-nutrients such as tannin, saponin and trypsin inhibitors remarkably reduced and hence the starch digestibility was improved. However, antioxidant compounds were degraded or lost, leading to lower antioxidant capacities in terms of 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) free radical scavenging ability and ferric reducing antioxidant power (FRAP). On the other hand, germination resulted in lesser reduction of anti-nutrients but lesser losses of antioxidants and good starch digestibility. Meanwhile, roasting caused the least effects on flour characteristics but was still able to partially degrade anti-nutrients.
Bacterial cellulose (BC) materials were used for lipase immobilization to improve enzyme activity and stability. BC films produced by Komagataeibacter xylinus were first acetylated in an acetic anhydride/iodine system to convert their OH groups to more hydrophobic acetyl groups. Activity yield (44.4%) and maximum specific activity (12.44 μmol mg–1 min–1) were achieved when 400 mg of BC was acetylated in 20 mL of acetic anhydride containing 0.275 mM of iodine. Studies on the catalytic activity of lipase also show that the immobilization of lipase on acetylated BC (ABC) films significantly enhanced its tolerance to temperature and pH. Immobilized lipases retained 89% and 56% of their catalytic activities after being incubated at 60 °C and 80 °C for 1 h, respectively; while those of free lipases significantly decreased to 24% (60 °C) and only 11% (80 °C). Immobilized lipases incubated at pH 5.0 and pH 10.0 for 24 h also retained high catalytic activities (70% and 82%, respectively), considerably higher than those of free lipases (19% - pH 5.0 and 63% - pH 10.0). Tolerance to organic solvents, such as n-hexane, acetone, ethanol, isopropanol of ABC-immobilized lipase was also improved. The immobilization of lipase on ABC films significantly improved its reusability and storage stability: ABC-immobilized lipase still could be reused for 30 cycles with residual activities of more than 90%, and still retained 95% of its early activity after 15-day storage at 4 °C. This implies that ABC-immobilized lipase is potentially applied in food, medicine, biodiesel and detergent industries.
The aim of this research was to investigate the effect of thermal treatments, including roasting, microwaving, and steaming, on anti-nutritional factors and physical and antioxidant properties of black gram (Vigna cylindrica L. Skeels). Regarding its physical properties, thermal treatment increased the water-holding capacity (WHC) and decreased the oil-holding capacity (OHC) of the black gram samples. No significant difference was observed between the roasted sample and the control. Regarding the chemical properties, anthocyanins accounted for the vast majority of total phenolic content (TPC). The steamed sample had the lowest TPC and anthocyanin values, which were 272.46 mg/100 g dry basis and 121.20 mg/100 g dry basis, respectively. Among the three types of thermal treatments, roasting resulted in the highest TPC content, which was 424.35 mg/100 g dry basis. Particularly, the steaming treatment led to the lowest anthocyanin content and antioxidant capacity (AC) in the flour sample; furthermore, there were no significant differences in the TPC and AC values between the microwaved and roasted samples. The phytate content was significantly reduced in all heat-treated samples and there were no significant differences among these cooked samples. The tannin content of the steamed sample was recorded to be the lowest, which was 164.19 mg/100 g dry basis. In summary, roasting, microwaving, and steaming significantly influenced the nutritive values of black gram (Vigna cylindrica L. Skeels).
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