Kwonsu Jung

Ethanol production from marine algal hydrolysates using Escherichia coli KO11.

Algae biomass is a potential raw material for the production of biofuels and other chemicals. In this study, biomass of the marine algae, Ulva lactuca, Gelidium amansii,Laminaria japonica, and Sargassum fulvellum, was treated with acid and commercially available hydrolytic enzymes. The hydrolysates contained glucose, mannose, galactose, and mannitol, among other sugars, at different ratios. The Laminaria japonica hydrolysate contained up to 30.5% mannitol and 6.98% glucose in the hydrolysate solids. Ethanogenic recombinant Escherichia coli KO11 was able to utilize both mannitol and glucose and produced 0.4g ethanol per g of carbohydrate when cultured in L. japonica hydrolysate supplemented with Luria-Bertani medium and hydrolytic enzymes. The strategy of acid hydrolysis followed by simultaneous enzyme treatment and inoculation with E. coli KO11 could be a viable strategy to produce ethanol from marine alga biomass.

Bioprocessing aspects of fuels and chemicals from biomass

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.

Volatile fatty acids derived from waste organics provide an economical carbon source for microbial lipids/biodiesel production

Volatile fatty acids (VFAs) derived from organic waste, were used as a low cost carbon source for high bioreactor productivity and titer. A multi‐stage continuous high cell density culture (MSC‐HCDC) process was employed for economic assessment of microbial lipids for biodiesel production. In a simulation study we used a lipid yield of 0.3 g/g‐VFAs, cell mass yield of 0.5 g/g‐glucose or wood hydrolyzates, and employed process variables including lipid contents from 10–90% of cell mass, bioreactor productivity of 0.5–48 g/L/h, and plant capacity of 20000–1000000 metric ton (MT)/year. A production cost of USD 1.048/kg‐lipid was predicted with raw material costs of USD 0.2/kg for wood hydrolyzates and USD 0.15/kg for VFAs; 9 g/L/h bioreactor productivity; 100, 000 MT/year production capacity; and 75% lipids content. The variables having the highest impact on microbial lipid production costs were the cost of VFAs and lipid yield, followed by lipid content, fermenter cost, and lipid productivity. The cost of raw materials accounted for 66.25% of total operating costs. This study shows that biodiesel from microbial lipids has the potential to become competitive with diesels from other sources.

Multi-stage continuous high cell density culture systems: a review.

A multi-stage continuous high cell density culture (MSC-HCDC) system makes it possible to achieve high productivity together with high product titer of many bioproducts. For long-term continuous operation of MSC-HCDC systems, the cell retention time and hydraulic retention time must be decoupled and strains (bacteria, yeast, plant, and animal cells) must be stable. MSC-HCDC systems are suitable for low-value high-volume extracellular products such as fuel ethanol, lactic acid or volatile fatty acids, and high-value products such as monoclonal antibodies as well as intracellular products such as polyhydroxybutyric acid (PHB), microbial lipids or a number of therapeutics. Better understanding of the fermentation kinetics of a specific product and reliable high-density culture methods for the product-generating microorganisms will facilitate timely industrialization of MSC-HCDC systems for products that are currently obtained in fed-batch bioreactors.