High cell density ethanol fermentation in an upflow packed-bed cell recycle bioreactor, Biotechnol Bioprocess Eng

Biotechnology and Bioprocess Engineering (Impact Factor: 1.11). 04/2008; 13(2):123-135. DOI: 10.1007/s12257-008-0004-9


An upflow packed-bed cell recycle bioreactor (IUPCRB) is proposed for obtaining a high cell density. The system is comprised
of a stirred tank bioreactor in which cells are retained partially by a packed-bed. A 1.3 cm (ID) × 48 cm long packed-bed
was installed inside a 2 L bioreactor (working volume 1 L). Continuous ethanol fermentation was carried out using a 100 g/L
glucose solution containing Saccharomyces cerevisiae (ATCC 24858). Cell retention characteristics were investigated by varying the void fraction (VF) of the packed bed by packing
it with particles of 0.8∼2.0 mm sized stone, cut hollow fiber pieces, ceramic, and activated carbon particles. The best results
were obtained using an activated carbon bed with a VF of 30∼35%. The IUPCRB yielded a maximum cell density of 87 g/L, an ethanol
concentration of 42 g/L, and a productivity of 21 g/L/h when a 0.5 h−1 dilution rate was used. A natural bleeding of cells from the filter bed occurred intermittently. This cell loss consisted
of an average of 5% of the cell concentration in the bioreactor when a high cell concentration (approximately 80 g/L) was
being maintained.

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    • "Multi-stage continuous high cell density culture (MSC-HCDC) is considered to be a fermentation technology that can lead to high productivity and titer for both extracellular and intracellular products [9] [10]. High cell density culture fermentation gives a very high productivity because of its high cell density achieved by membrane cell recycling, or a moderate cell density attained by using a packed-bed combined with gravity settling [11] [12] [13] [14]. Fei et al. [15] [16] achieved a lipid content of 55% (w/w) using VFAs as a carbon source in two-stage cultivation. "
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    ABSTRACT: Volatile fatty acids (VFAs) derived from waste organics were used as low cost carbon source, for high bioreactor productivity and titer, and multi-stage continuous high cell density culture (MSC-HCDC) process was employed for economic assessment of microbial lipids for biodiesel production. The simulation study used a lipid yield of 0.3g/g-VFAs, cell mass yield of 0.5g/g-glucose or wood hydrolyzates, and employed process variables of carbon sources including lipid contents from 10∼90% of cell mass, bioreactor productivity of 0.5∼48g/L/h, and plant capacity of 20,000∼1,000,000 MT/year. A $1.048/kg-lipid was predicted with $0.2/kg wood hydrolyzates and $0.15/kg VFAs; 9g/L/h bioreactor productivity; 100,000 MT/year production capacity; and 75% lipids content. The variables affecting the microbial lipid cost were the cost of VFAs and lipid yield followed by lipid content, fermenter cost and lipid productivity. The raw materials costs accounted for 66.25% of total operating costs. Biodiesel from microbial lipids has a potential to become competitive with diesels from other sources.
    Full-text · Article · Dec 2014 · Biotechnology Journal
    • "In addition, because of the low release of CO 2 during anaerobic fermentation, mixed VFA fermentation provides a higher carbon yield than direct ethanol fermentation using yeast or Zymomonas mobilis (Bolzonella et al., 2005; Chang et al., 2008). Thus, if VFAs can be converted to fuels and chemicals such as ethanol and butanol via economical processes, mixed VFA fermentation could provide a new platform with versatile applications for the production of biofuels. "
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    ABSTRACT: Volatile fatty acids (VFA) are promising biofuel precursors that can be processed to produce mixed alcohols or other biofuels. This study evaluates the economy of production and separation of VFAs as products of anaerobic digestion (AD) of brown algae. Membrane distillation (MD) was integrated to product recovery unit to increase the VFA concentration from 3% to 10% in fermentation broth. The process is simulated in Aspen Plus v8.4 and a techno-economic model were developed to calculate minimum VFA selling price. The results showed profitability of using membrane distillation to lower the utility and operation costs of VFA recovery. A minimum VFA selling price of 384 $/t were calculated for base case. A sensitivity analysis on permeate flux and cost were performed to cover uncertainties in MD unit. The lower cost obtained for VFA production in this study makes brown algae a reliable candidate for VFA and subsequent biofuel production processes.
    No preview · Conference Paper · Jul 2014
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    ABSTRACT: This review deals with a recent development of biofuels and chemicals from biomass. Some of the grainbased biofuels and chemicals have already been in commercial operation, including fuel ethanol, biodiesel, 1.3-propanediol, polylactic acid (PLA) and polyhydroxy butyric acid/alkanoates (PHB/PHA). The next generation bioproducts will be based on lignocellulosics due to their abundance and to stabilize rising food prices. However, the technologies of handling biomass are yet in their infancy and suffer from low yield, low product titer, and low productivity. This review focuses on bioprocessing technologies for biofuels production: organic raw biomaterials available in Korea; volatile fatty acids platform, multi-stage continuous high cell density culture (MSC-HCDC), enrichment of fermentation broth by forward osmosis; various purification methods of pervaporation of ethanol, solvent extraction on succinic, lactic acids and reactive separation methods.
    No preview · Article · Jul 2012 · Korean Journal of Chemical Engineering
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