Use Of Lignocellulose Research Articles

Lactic acid production from lignocellulose-derived sugars using lactic acid bacteria: Overview and limits

Lactic acid is an industrially important product with a large and rapidly expanding market due to its attractive and valuable multi-function properties. The economics of lactic acid production by fermentation is dependent on many factors, of which the cost of the raw materials is very significant. It is very expensive when sugars, e.g., glucose, sucrose, starch, etc., are used as the feedstock for lactic acid production. Therefore, lignocellulosic biomass is a promising feedstock for lactic acid production considering its great availability, sustainability, and low cost compared to refined sugars. Despite these advantages, the commercial use of lignocellulose for lactic acid production is still problematic. This review describes the "conventional" processes for producing lactic acid from lignocellulosic materials with lactic acid bacteria. These processes include: pretreatment of the biomass, enzyme hydrolysis to obtain fermentable sugars, fermentation technologies, and separation and purification of lactic acid. In addition, the difficulties associated with using this biomass for lactic acid production are especially introduced and several key properties that should be targeted for low-cost and advanced fermentation processes are pointed out. We also discuss the metabolism of lignocellulose-derived sugars by lactic acid bacteria.

Sustainable transportation second generation liquid biofuels: The way forward

With the potential depletion of liquid fuels, a search is on for alternative renewable liquid fuels in the transportation sector. While first generation biofuels produced from starch based materials are already available, it is considered to have direct and indirect effects on food security. The bioconversion of lignocellulosic residues is considered an appropriate alternative as it does not affect food security and in many cases has a positive carbon balance from a climate point of view. This paper highlights the major advances and barriers to the use of lignocellulosics for the production of bioethanol. Starting with land use patterns, the bottlenecks to technical conversion of these residues and by-products, specifically the pretreatment and saccharification steps, are presented in a concise manner. The way in which subsidies affect the cost of the product, which is not economically feasible at current petroleum prices, the possibility of using the different products produced in the overall conversion stages, and the need to make complete life cycle analysis, on a case by case basis, to determine the effects on the atmosphere are highlighted.

Deletion of methylglyoxal synthase gene (mgsA) increased sugar co-metabolism in ethanol-producing Escherichia coli

The use of lignocellulose as a source of sugars for bioproducts requires the development of biocatalysts that maximize product yields by fermenting mixtures of hexose and pentose sugars to completion. In this study, we implicate mgsA encoding methylglyoxal synthase (and methylglyoxal) in the modulation of sugar metabolism. Deletion of this gene (strain LY168) resulted in the co-metabolism of glucose and xylose, and accelerated the metabolism of a 5-sugar mixture (mannose, glucose, arabinose, xylose and galactose) to ethanol.

Novel Evolutionary Engineering Approach for Accelerated Utilization of Glucose, Xylose, and Arabinose Mixtures by Engineered Saccharomyces cerevisiae Strains

Lignocellulosic feedstocks are thought to have great economic and environmental significance for future biotechnological production processes. For cost-effective and efficient industrial processes, complete and fast conversion of all sugars derived from these feedstocks is required. Hence, simultaneous or fast sequential fermentation of sugars would greatly contribute to the efficiency of production processes. One of the main challenges emerging from the use of lignocellulosics for the production of ethanol by the yeast Saccharomyces cerevisiae is efficient fermentation of D-xylose and L-arabinose, as these sugars cannot be used by natural S. cerevisiae strains. In this study, we describe the first engineered S. cerevisiae strain (strain IMS0003) capable of fermenting mixtures of glucose, xylose, and arabinose with a high ethanol yield (0.43 g g(-1) of total sugar) without formation of the side products xylitol and arabinitol. The kinetics of anaerobic fermentation of glucose-xylose-arabinose mixtures were greatly improved by using a novel evolutionary engineering strategy. This strategy included a regimen consisting of repeated batch cultivation with repeated cycles of consecutive growth in three media with different compositions (glucose, xylose, and arabinose; xylose and arabinose; and only arabinose) and allowed rapid selection of an evolved strain (IMS0010) exhibiting improved specific rates of consumption of xylose and arabinose. This evolution strategy resulted in a 40% reduction in the time required to completely ferment a mixture containing 30 g liter(-1) glucose, 15 g liter(-1) xylose, and 15 g liter(-1) arabinose.

Study of the conditions of enzyme formation and the secretion of extracellular ligninases by the funguspleurotus ostreatus UzBI-1108

The possibility has been shown of the rational use of lignocellulose wastes as components of a nutrient medium for the deep cultivation of some wood-destroying basidial fungi isolated from various sources and actively breaking down natural polysaccharides and lignin with the formation of ligninolytic enzymes and biologically valuable products. An active producing agent of ligninolytic enzymes (laccase, peroxidase, lignin peroxidase, polyphenoloxidase, Mn-dependent peroxidase) has been revealed as Pleuroms ostreatus, strain UzBI-I108. The optimum conditions have been determined for the formation of enzymes and the secretion of total ligninase preparations with a fairly high specific activity of lignin peroxidase.

Technical and economic analysis of lignin conversion to methyl aryl ethers

The economical use of lignocellulosics for the production of liquid fuel depends on the efficient utilization of all the components in the feed material. Lignin can be converted to methyl aryl ethers (MAE’s), products with blending octane numbers and Reid vapor pressures that make them excellent candidates for use as octane enhancers in gasoline.