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Bio-oil Production through Hydrothermal Liquefaction (HTL) of Biomass
Published in Ozcan Konur, Biodiesel Fuels, 2021
Leichang Cao, Daniel C. W. Tsang, Shicheng Zhang
Protein is the main source of nitrogen heterocyclic compounds in bio-oils (Gu et al., 2020; Teri et al., 2014). At temperatures of 0–100°C, proteins undergo hydrolysis reactions to form various amino acids. As the temperature rises, various reactions occur in the generated amino acids. The decarboxylation and the deamination are the two main reactions and, between 100 and 200°C, carboxyl functional groups in some amino acids are decarboxylated to form amine compounds, in which carboxyl groups are released as gas-phase products, such as CO2 (Teri et al., 2014). Another part of the amino acid is formed into organic acid through a deamination reaction, in which the amino group is released in the form of NH3. In addition, the amino acid may undergo a Maillard reaction’ with a carbohydrate hydrolysate such as reducing sugars to form a variety of heterocyclic nitrogen oxides, including pyrrole, pyrrolidone, pyridine, and imidazole, and finally to form a nitrogen-rich polymerized substance which is called melanin (Feng et al., 2018).
Enzyme Catalysis
Published in Harvey W. Blanch, Douglas S. Clark, Biochemical Engineering, 1997
Harvey W. Blanch, Douglas S. Clark
Electrophilic catalysts, in contrast to nucleophilic catalysis, act by withdrawing electrons from the reaction center of the intermediate and are thus electron sinks. They stabilize a negative charge. Examples of this mechanism involve coenzymes thiamine pyrophosphate and pyridoxal phosphate. In many cases, including these coenzymes, electrophilic catalysis involves the formation of Schiff bases. For example, acetoacetate decarboxylase catalyzes the decarboxylation of acetoacetate to acetone and CO2. The mechanism involves the formation of a Schiff base involving a lysine residue.
Postharvest blanching and drying of industrial hemp (Cannabis sativa L.) with infrared and hot air heating for enhanced processing efficiency and microbial inactivation
Published in Drying Technology, 2023
Chang Chen, Ke Wang, Ivan Wongso, Zhaokun Ning, Ragab Khir, Daniel Putnam, Irwin R. Donis-González, Zhongli Pan
The total CBD contents of the dried hemp samples in this study were 13.76 ± 0.10, 13.79 ± 0.15, 13.46 ± 0.13, 13.65 ± 0.09, 13.54 ± 0.16 g/100g dried biomass, under “Conventional,” “HA-65 °C,” “HA-85 °C,” “IR 1 min-HA 65 °C” and “IR 2 min-HA 65 °C,” respectively, which were equal to 98.2%, 98.4%, 96.1%, 97.4% and 96.7% to that in the fresh hemp biomass. With the increase in the drying temperature, the contents of CBDA decreased while the contents of CBD increased. The values of the CBDA conversion ranged from 0.29% to 11.88% under the tested conditions (Figure 3C). The results indicated the conversion of CBDA into CBD, which has been known as the decarboxylation reaction under high temperature processing. IR preheating before HA drying led to higher levels of decarboxylation from CBDA to CBD, which should be due to the higher sample temperature achieved during the IR heating period (Figure 2C and 2D). According to Singh et al.,[28] the kinetics of the decarboxylation reaction was significantly affected by the heating temperature. A higher temperature normally results in a faster the rate of decarboxylation. Under the tested conditions, the influence of drying temperature on the CBDA contents was statistically significant (p < 0.01). However, the influence of drying conditions on the total CBD contents was not statistically significant (p > 0.01).