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Conventional solvent extraction methods cannot attain high‐quality antioxidant extracts from microalgae and also require solvent recovery and posttreatment. In this study, we utilized environmental friendly supercritical carbon dioxide fluid extraction (SFE‐CO2) techniques to obtain pigment (i.e. astaxanthin) from Haematococcus pluvialis. The effects of key operating parameters on the extraction efficiency of astaxanthin were investigated, giving an optimal condition of H. pluvialis weight, 6.5 g; CO2‐flow rate, 6.0 NL/min; extraction time, 20 min; extraction pressure, 4500 psi; volume of ethanol modifier added, 9.23 mL/g; extraction temperature, 50°C; modifier composition, 99.5%. Under these optimum conditions, the astaxanthin yield was 73.9% (10.92 mg/g dry H. pluvialis powder) after eight cycle of extraction cycles. The saponification index (CS/C0, representing the ratio of astaxanthin concentration after and before the saponification procedures) of the extract could be increased from 1 to 12.78 by saponification with 3.5 M NaOH.

Response surface methodology (RSM) was used to compare the effects of the selected variables on the changes of concentrations of limonene,α‐terpineol and carvone by ultra‐high hydrostatic pressure (UHP) treatment. A Box–Behnken experimental design was used with control variables of pressure (100–500 MPa), temperature (20–40C) and treatment time (10–20 min). Pressure, temperature and treatment time were found to be critical factors influencing changes of concentrations. Both pressure and temperature could cause limonene degradation, resulting in significant increase ofα‐terpineol and carvone concentrations. Limonene degradation was increased with increasing processing pressure or temperature. An interaction effect of pressure and temperature on limonene degradation was also found. This study showed that Box–Behnken design and RSM could be used to model the changes in concentrations of limonene,α‐terpineol and carvone in orange juice by UHP treatment. PRACTICAL APPLICATIONS As we know, ultra‐high hydrostatic pressure (UHP) processing has been an attractive way to replace conventional heat treatments for the preservation of foods. In our study, models of changes in the key aroma compounds in orange juice under UHP process were established. The changes of these aroma compounds in orange juice under UHP process could be understood further by these models. An improved understanding of the effect of UHP on critical aroma quality compounds of orange juices was helpful for us to facilitate industrial adoption of this technology. An effective research way to study the effect on aroma compounds by UHP process was also offered. Base on the data, there was a reference for us to establish an establishment of UHP processing criteria for commercial production of high‐aroma‐quality orange juice.

Penicillin G acylase (PGA) is an important enzyme for the industrial production of 7-amino-3-deacetoxy cephalosporanic acid (7-ADCA) from cephalosporin G (Ceph-G), and 6-aminopenicillanic acid (6-APA) from penicillin G (Pen-G). These products are used for the manufacture of semi-synthetic cephalosporins and penicillins. In this study, immobilized PGA was utilized to catalyze the conversion of Ceph-G to 7-ADCA. The optimal conditions were found to be an operating temperature of 45• C, 0.2 M phosphate buffer, a substrate concentration of 30 mg cm −3 and a catalyst particle concentration of 0.01 g cm −3 (specific activity of 623.2 U g −1 ). Up to 45• C the reaction was characterized by an activation energy of 38.66 kJ mol −1 . Beyond 57.5• C there was a sharp decline of activity, characterized by a deactivation energy of 235.88 kJ mol −1 .