High Cell Density Cultivation of Saccharomyces cerevisiae with Intensive Multiple Sequential Batches Together with a Novel Technique of Fed-Batch at Cell Level (FBC)

Abstract

High cell density cultivation (HCDC) is developed for the production of microbial biomasses and their products. They must be produced from high concentrations of substrate, e.g., glucose or sucrose. In batch culture, a high concentration of those sugars >40–50% (w/v) cannot efficiently be utilized because of a dissolved O2 limitation causing the Crabtree effect that produces toxic by-products, i.e., ethanol and/or acetate, that inhibit cell growth. To prevent this effect, the HCDC is conducted with the fed-batch strategies. However, it has many disadvantages, i.e., complicated operations. To overcome those problems, this study was designed to use a new, efficient C-source (carbon source) substrate, namely dextrin, an oligomer of glucose. It can be utilized by yeast at a very high concentration of ~100 g/L although using just batch cultivation. As it is gradually hydrolyzed to release glucose molecules and gradually assimilated into the cells as “fed-batch at the cell level” (FBC), it prevents the yeast cell system from undergoing the Crabtree effect. In this research, the types of medium, the types of sugar compared with dextrin, and the concentrations of yeast extract (YE) were studied. The batch production medium (BPM) with dextrin and YE performed very good results. The concentrations of dextrin for yeast cultivation were studied in the aerobic batch 5-L bioreactors. Its optimum concentration was at 90 g/L with 9 g/L of YE in 3× BPM. It was operated at 3 W/kg energy dissipation rate per unit mass (ε¯T) and 3 vvm airflow rate. Further, the intensive multiple sequential batch (IMSB) technique of high intensities of agitation speed and airflow was developed to achieve higher yield and productivity. The maximum values of cell biomass, specific growth rate, yield coefficient, productivity, and efficiency were at 55.17 g/L, 0.21 h−1, 0.54 g/g, 2.30 g/L/h, and 98.18%, respectively. The studies of cell growth kinetics, biochemical engineering mass balances, and fluid dynamics for the design of impeller speeds of the 5-L bioreactors during the cultivations of yeast using dextrin at the high concentrations were successful. The results can be used for the scale-up of bioreactor for the industrial production of yeast cell biomass at high concentrations.

Single-step ethanol production from raw cassava starch using a combination of raw starch hydrolysis and fermentation, scale-up from 5-L laboratory and 200-L pilot plant to 3000-L industrial fermenters

“…Analyses were performed at 60 °C. Samples were diluted 10 times, filtered through 0.45-µm filters, and injected into the column with an amount of 20 µL [ 27 , 45 ] .…”

“…Neutralizations were done with the addition of 4 N NaOH and re-centrifugations were operated to precipitate residues. Supernatants were analyzed using the HPLC to quantify concentrations of glucose as the total sugar [ 27 , 45 ] .…”

“…(iii) The utilization rate of substrate, r s (g/L/h) is from . The production efficiency, Ef (%) is from Ef , where Y p/s is from the experiment (observed value) and Y' p/s is from the theoretical yield coefficient or stoichiometry [ 45 ]. The theoretical yield, Y' p/s of ethanol from starch is 0.566 g/g, calculated from , where “a” is the glucose yield of 1.11 g from 1.00 g of starch as in Eq.…”

Novel Strategy for the Calorimetry-Based Control of Fed-Batch Cultivations of Saccharomyces cerevisiae

“…Previously steady-state control responses were reported for feed-forward/feedback PI controller simulations of fed-batch microbial bioprocess models [27]. Some progress has been made to apply a control methodology to high-concentration S. cerevisiae bioprocesses, including merging multiple batch-processes within a fed-batch optimization [28].…”

Advances in Microbial Fermentation Processes

“…The novel cell-level Fed-Batch (FBC) technology for the high-cell-density cultivation of Saccharomyces cerevisiae was proposed by Malairuang et al [11] with a clear illustration of the principle of operation, the potential dextrin substrate, and the mechanism of substrate utilization to regulate FBC, FBC kinetics and material balances through a bioreactor design and scale-up. Yepes-García and coworkers [12] provided an important contribution to the knowledge of antibiotic biosynthesis in the Streptomyces genus by studying the relationship between S. clavuligerus ATCC 27064 morphology and CA biosynthesis.…”