Integrated bioprocessing for plant cell cultures

Strategies for improving the production of bio-based vanillin

Vanillin (4-hydroxy-3-methoxybenzaldehyde) is one of the most popular flavors with wide applications in food, fragrance, and pharmaceutical industries. However, the high cost and limited yield of plant extraction failed to meet the vast market demand of natural vanillin. Vanillin biotechnology has emerged as a sustainable and cost-effective alternative to supply vanillin. In this review, we explored recent advances in vanillin biosynthesis and highlighted the potential of vanillin biotechnology. In particular, we addressed key challenges in using microorganisms and provided promising approaches for improving vanillin production with a special focus on chassis development, pathway construction and process optimization. Future directions of vanillin biosynthesis using inexpensive precursors are also thoroughly discussed.

Use of Model-Based Nutrient Feeding for Improved Production of Artemisinin by Hairy Roots of Artemisia Annua in a Modified Stirred Tank Bioreactor

Artemisinin has been indicated to be a potent drug for the cure of malaria. Batch growth and artemisinin production kinetics of hairy root cultures of Artemisia annua were studied under shake flask conditions which resulted in accumulation of 12.49 g/L biomass and 0.27 mg/g artemisinin. Using the kinetic data, a mathematical model was identified to understand and optimize the system behavior. The developed model was then extrapolated to design nutrient feeding strategies during fed-batch cultivation for enhanced production of artemisinin. In one of the fed-batch cultivation, sucrose (37 g/L) feeding was done at a constant feed rate of 0.1 L/day during 10-15 days, which led to improved artemisinin accumulation of 0.77 mg/g. The second strategy of fed-batch hairy root cultivation involved maintenance of pseudo-steady state sucrose concentration (20.8 g/L) during 10-15 days which resulted in artemisinin accumulation of 0.99 mg/g. Fed-batch cultivation (with the maintenance of pseudo-steady state of substrate) of Artemisia annua hairy roots was, thereafter, implemented in bioreactor cultivation, which featured artemisinin accumulation of 1.0 mg/g artemisinin in 16 days of cultivation. This is the highest reported artemisinin yield by hairy root cultivation in a bioreactor.

Efficient production and recovery of diterpenoid tanshinones in Salvia miltiorrhiza hairy root cultures with in situ adsorption, elicitation and semi-continuous operation

In Salvia miltiorrhiza hairy root cultures, the desired secondary metabolites diterpenoid tanshinones are normally produced at low yields and stored within the roots. To enhance tanshinone production and the secondary product recovery, we employed three means, elicitation with a yeast elicitor (YE), in situ adsorption of tanshinones with a hydrophobic polymeric resin (X-5) and semi-continuous mode of operation. YE treatment stimulated the tanshinone biosynthesis, increasing the total tanshinone (TT) content of root by about two-fold, from 0.46 to 1.37 mg/g dry weight (dw) (TT content=total content of three major tanshinones, cryptotanshinone, tanshinone I and tanshinone IIA). The addition of X-5 resins to the culture only increased the tanshinone yield slightly, but recovered more than 80% of tanshinones from the roots. With the application of a semi-continuous culture process involving repeated medium renewal, elicitor addition and resin replacement, starting at the late exponential growth phase, the root biomass was increased to 30.5g dw/l (versus 8-10g dw/l in batch mode) and the volumetric tanshinone yield to 87.5mg/l (about 15-fold increase), with 76.5% adsorbed to the resin. The volumetric productivity of total tanshinone reached 1.46 mg/lday, more than 7.4 times that of the batch culture. The results demonstrate that the integration of multiple elicitation, in situ adsorption and semi-continuous operation can synergistically enhance tanshinone production in S. miltiorrhiza hairy root cultures.

Integrated isolation of antibody fragments from microbial cell culture fluids using supermacroporous cryogels

The present paper describes a chromatographic capture/purification step for the recovery of proteins directly from undiluted and unclarified cell culture broths using supermacroporous dimethylacrylamide (DMAA) cryogel. The interconnected character and the size (10-100 microm) of the pores of the adsorbent make it possible to process whole cell fermentation broths without blocking the column. Cu2+-iminodiacetic acid (IDA) DMAA cryogel has been used for the isolation and purification of excreted (His)6-tagged single chain (sc) Fv antibody fragments, (His)6-scFv, from E. coli cell culture. Bound protein was recovered with 0.2 M imidazole or with 20 mM EDTA and was practically cell-free. Chromatographic capture using Cu2+-IDA cryogel column was performed at flow rates of 300 and 600 cm/h, respectively and resulted in 84-96% recovery of (His)6-scFv fragments with a purification factor of 13-15. The DMAA cryogel adsorbent is mechanically stable, can withstand harsh cleaning-in-place procedure and is relatively inexpensive. Chromatographic isolation of proteins using cryogels allows efficient removal of cells and can be operated at a flow rate as high as 600 cm/h. This novel technique has proven to be a scalable process, does not require special equipment and can be a good alternative to expanded bed adsorption and other integrated isolation techniques.