•Continuous production of GOS from a lactose in an UMR.•Purification of GOS with the NF membrane in a continuous diafiltration process.•Continuous production of high-purity GOS in the CPNSS.Continuous enzymatic production of galactosyl-oligosaccharides (GOS) from a lactose substrate in an ultrafiltration membrane reactor (UMR) coupled with a nanofiltration separation system (CPNSS) was investigated. The overall rate of production over 4 h of continuous production was 80–104 mg GOS formed/U with an average residence time of 66 min, an initial lactose concentration of 300 g/L, an inlet pressure of 2.0 bar inlet pressure, and an outlet pressure of 1.5 bar. In the continuous diafiltration (CD) process, the concentration of various sugars and the relationship between the yield and purity of oligosaccharides was well predicted by mathematical models, the increased rate of sugar rejections was less than 10%, and the decreased rate of concentrations in the tank was less than 15%. In the CPNSS, 33.4 wt.% GOS was obtained in the UMR, and 1.24 kg of high-purity GOS (specifically, GOS purity of 57.2% and lactose content less than 20%) was achieved. This final yield was 80.1% GOS, which meets industry standards.

In this study, a fibrous matrix with chemical modification was used as a support material for the immobilization of Saccharomyces cerevisiae 1308. Cassava hydrolysate without filteration was used for ethanol fermentation. An average utilization rate of starch of 83.5% was obtained by the immobilized cells during the first seven repeated simultaneous saccharification and fermentation. The utilization rate of starch of the immobilized cells was 2.1% higher than that of free cells with an inoculation quantity of 15% (v/v) under the same fermentation conditions. In addition, the effects of enzyme feeding strategies on immobilized yeast fermentation were investigated. The highest utilization rate of starch of 85.9% was obtained at 35 °C with the optimal enzyme feeding strategy. Fermentation performed successfully for about 6 months with 87 batches suggests that ethanol production from cassava using immobilized yeast in a fibrous-bed bioreactor is feasible and may meet the demands of industrial production.

The efficiency of current methods for industrial production of the enzyme nuclease P1 is limited. In this study, we sought to improve fermentation methods for the production of nuclease P1. An immobilized fermentation system using an activated carbon filter sponge as a carrier was used for the production of nuclease P1. In an airlift internal loop reactor (ALR), the fermentation performance of three different fermentation modes, including free-cell fermentation, repeated-batch fermentation, and semi-continuous immobilized fermentation, were compared. The fermentation kinetics in the fermentation broth of the three fermentation modes, including dissolved oxygen (DO), pH value, cell concentration, residual sugar concentration, and enzyme activity, were tested. The productivity of semi-continuous immobilized fermentation reached 8.76 U/mL/h, which was 33.3 and 80.2 % higher than that of repeated-batch fermentation and free-cell fermentation, respectively. The sugar consumption of free-cell, repeated-batch, and semi-continuous immobilized fermentations was 41.2, 30.8, and 25.9 g/L, respectively. These results showed that immobilized-cell fermentation by using Penicillium citrinum with activated carbon filter sponge in an ALR was advantageous for nuclease P1 production, especially in the semi-continuous immobilized fermentation mode. In spite of the significant improvement in nuclease P1 production in semi-continuous immobilized fermentation mode, the specific activity of nuclease P1 was almost equal among the three fermentation modes.