Lipase Catalyzed Synthesis of ABA-Type Structured Lipid from Single Cell Oil and Tripalmitin

Recent Development of Advanced Biotechnology in the Oleaginous Fungi for Arachidonic Acid Production

Arachidonic acid is an essential ω-6 polyunsaturated fatty acid, which plays a significant role in cardiovascular health and neurological development, leading to its wide use in the food and pharmaceutical industries. Traditionally, ARA is obtained from deep-sea fish oil. However, this source is limited by season and is depleting the already threatened global fish stocks. With the rapid development of synthetic biology in recent years, oleaginous fungi have gradually attracted increasing attention as promising microbial sources for large-scale ARA production. Numerous advanced technologies including metabolic engineering, dynamic regulation of fermentation conditions, and multiomics analysis were successfully adapted to increase ARA synthesis. This review summarizes recent advances in the bioengineering of oleaginous fungi for ARA production. Finally, perspectives for future engineering approaches are proposed to further improve the titer yield and productivity of ARA.

The effects of interesterification on the physicochemical properties of Pangasius bocourti oil and its fractions

Soft and solid fats which were fractionated from Pangasius bocourti oil (PBO), namely, Pangasius bocourti olein (PBOL) and Pangasius bocourti stearin (PBST), respectively, were introduced as new base oils for plastic fats. The physicochemical properties of PBO and its fractions were modified after interesterification. Enzymatic interesterification (EIE) reduced the sn-2 palmitic acid content attributed to the occurrence of acyl migration. The PBO solid fat content (SFC) at 20-40 °C increased after chemical interesterification whereas under similar range of temperature, the SFC of PBST decreased after EIE and a steep melting curve was obtained. The effect of interesterification on the crystal polymorphisms was less prominent whereby the initial and interesterified samples exhibited similar crystal forms. The solid state of PBOL was improved after interesterification but post-hardening was observed. Free fatty acids were produced via partial hydrolysis during EIE which contributed to the reduced oxidative stability in the EIE fats.

Enzymatic Interesterification of Palm Stearin and Palm Olein Blend Catalyzed by sn-1,3-Specific Lipase: Interesterification Degree, Acyl Migration, and Physical Properties

Acyl migration of fatty acid at sn-2 is often observed alongside enzymatic interesterification (EIE), causing the loss of lipase selectivity toward the acyl group at sn-1,3. In this study, an oil blend consisting of palm stearin (PST) and palm olein (POL) was interesterified via a chemical interesterification (CIE) and enzymatic method using a packed bed reactor. Characterization in terms of the triacylglycerol (TAG) compositions, sn-2 fatty acid distributions, and solid fat content profiles was performed. In comparison to that of CIE fats, EIE fats showed different modification effects on the solid fat content. Under similar reaction conditions, different interesterification degrees (IDs) were obtained according to the various blend ratios. Using the same mass ratio of substrates (POL/PST of 9:1), the EIE reaction time and temperature affected the ID and the change in the fatty acyl group at the sn-2 position. Under the reaction time of 46 min, an ID of 94.41% was acquired, while at 80 °C, the degree of acyl migration at sn-2 was 92.87%. EIE with high acyl migration exhibited a lower crystallization rate than that of EIE with low acyl migration. However, the effect of acyl migration on crystal polymorphism and oxidative stability was insignificant. Outcomes from this study are meaningful for the establishment of a theoretical basis for a controlled positional-specific EIE that is catalyzed by sn-1,3-specific lipase.

Evaluation of enzymatic interesterification in structured triacylglycerols preparation: a concise review and prospect

Enzymatic interesterification (EIE) is one of the emerging technologies in the specialty fats industry. EIE has several advantages over the conventional chemical interesterification method, such that the process has higher flexibility and efficiency, is environmentally friendly and the immobilized enzyme can be recycled besides of the lower requirement for substrate's acid value. The physical properties and nutritional qualities of the fats and oils are modified after EIE, depending on the change in the position of fatty acids on the triacylglycerol (TAG) molecules. Evaluation of the interesterification reaction are important and useful in terms of its technological applications. This paper summarizes the conventional methods and the advancement for evaluating EIE processes, e.g., determination of the change in slip melting points, solid fat contents, TAG with equivalent carbon numbers, and sn-2 fatty acid compositions of the end product. Nonetheless, these methods are not comprehensive because during the EIE process, acyl migration occurs. A novel and convenient evaluation model which is based on the fatty acid distribution on the glycerol-backbone is proposed as a perspective. This model can be employed to monitor the interesterification degree and acyl migration during a regiospecific EIE process, which serves as a reaction rule that can be employed to control and optimize the EIE process, thereby producing structured TAG with desired properties.

A Density Functional Theory (DFT) Study of the Acyl Migration Occurring during Lipase-Catalyzed Transesterifications

Acyl migration (AM) is the main side reaction in the large-scale, regio-specific lipase catalyzed production of structural triglycerides (STs). A detailed understanding of the mechanism of AM was obtained during the process of lipase-catalyzed schemes (LCSs), which play a vital role in improving the quality and total yield of STs. However, currently, the mechanism of AM remains controversial. Herein, the two mechanisms (non-catalyzed (NCM) and lipase-catalyzed (LCM)) of AM have been analyzed in detail by the density functional theory (DFT) at the molecular level. Based on the computational results, we concluded that the energy barrier of the rate-limiting step in the LCM was 18.8 kcal/mol, which is more in agreement with the available experimental value (17.8 kcal/mol), indicating that LCM could significantly accelerate the rate of AM, because it has an energy barrier ~2 times lower than that of the NCM. Interestingly, we also found that the catalytic triad (Asp-His-Ser) of the lipase and water could effectively drop the reaction barrier, which served as the general acid or base, or shuttle of the proton.

Effect of intense pulsed light on the deactivation of lipase: Enzyme-deactivation kinetics and tertiary structural changes by fragmentation

The effect of intense pulsed light (IPL) irradiation on Chromobacterium viscosum lipase was investigated with a primary focus on catalytic activity and molecular structure. During IPL irradiation, lipase activity decreased significantly with increasing pulse fluence (F_p) and exposure time (t_e). IPL-induced deactivation kinetics were further elucidated based on a two-step series-type deactivation model (constant deactivation rate k₁ >k₂). F_p was found to be the dominant variable affecting the degree of lipase deactivation, and residual activity was not associated with increasing t_e below a certain F_p energy density (2.66 mJ/cm²), implying a critical threshold for IPL-induced deactivation of lipase. From the results of fluorescence spectroscopy and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), we determined that IPL-induced deactivation was caused by fragmentation, leading to lipase tertiary structural changes. Furthermore, the results of FindPept analysis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) indicated that the internal sensitive bonds of lipase were cleaved preferentially by IPL, such that IPL irradiation induced site-sensitive fragmentation and peptide bond cleavage.