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About: Fermentation is a(n) research topic. Over the lifetime, 68865 publication(s) have been published within this topic receiving 1251939 citation(s). The topic is also known as: fermentation (metabolism).
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Journal ArticleDOI
Abstract: During hydrolysis of lignocellulosic materials a wide range of compounds which are inhibitory to microorganisms are formed or released. Based on their origin the inhibitors are usually divided in three major groups: weak acids, furan derivatives, and phenolic compounds. These compounds limit efficient utilisation of the hydrolysates for ethanol production by fermentation. If the inhibitors are identified and the mechanisms of inhibition elucidated, fermentation can be improved by developing specific detoxification methods, choosing an adapted microorganism, or optimising the fermentation strategy. The present review discusses the generation of inhibitors during degradation of lignocellulosic materials, and the effect of these on fermentation yield and productivity. Inhibiting mechanisms of individual compounds present in the hydrolysates and their interaction effects are reviewed.

2,214 citations

Journal ArticleDOI
Yan Lin1, Shuzo Tanaka1Institutions (1)
TL;DR: The prospects included are fermentation technology converting xylose to ethanol, cellulase enzyme utilized in the hydrolysis of lignocellulosic materials, immobilization of the microorganism in large systems, simultaneous saccharification and fermentation, and sugar conversion into ethanol.
Abstract: In recent years, growing attention has been devoted to the conversion of biomass into fuel ethanol, considered the cleanest liquid fuel alternative to fossil fuels. Significant advances have been made towards the technology of ethanol fermentation. This review provides practical examples and gives a broad overview of the current status of ethanol fermentation including biomass resources, microorganisms, and technology. Also, the promising prospects of ethanol fermentation are especially introduced. The prospects included are fermentation technology converting xylose to ethanol, cellulase enzyme utilized in the hydrolysis of lignocellulosic materials, immobilization of the microorganism in large systems, simultaneous saccharification and fermentation, and sugar conversion into ethanol.

1,519 citations

Journal ArticleDOI
01 Jul 1992-Yeast
Abstract: Addition of benzoate to the medium reservoir of glucose-limited chemostat cultures of Saccharomyces cerevisiae CBS 8066 growing at a dilution rate (D) of 0.10 h-1 resulted in a decrease in the biomass yield, and an increase in the specific oxygen uptake rate (qO2) from 2.5 to as high as 19.5 mmol g-1 h-1. Above a critical concentration, the presence of benzoate led to alcoholic fermentation and a reduction in qO2 to 13 mmol g-1 h-1. The stimulatory effect of benzoate on respiration was dependent on the dilution rate: at high dilution rates respiration was not enhanced by benzoate. Cells could only gradually adapt to growth in the presence of benzoate: a pulse of benzoate given directly to the culture resulted in wash-out. As the presence of benzoate in cultures growing at low dilution rates resulted in large changes in the catabolic glucose flux, it was of interest to study the effect of benzoate on the residual glucose concentration in the fermenter as well as on the level of some selected enzymes. At D = 0.10 h-1, the residual glucose concentration increased proportionally with increasing benzoate concentration. This suggests that modulation of the glucose flux mainly occurs via a change in the extracellular glucose concentration rather than by synthesis of an additional amount of carriers. Also various intracellular enzyme levels were not positively correlated with the rate of respiration. A notable exception was citrate synthase: its level increased with increasing respiration rate. Growth of S. cerevisiae in ethanol-limited cultures in the presence of benzoate also led to very high qO2 levels of 19-21 mmol g-1 h-1. During growth on glucose as well as on ethanol, the presence of benzoate coincided with an increase in the mitochondrial volume up to one quarter of the total cellular volume. Also with the Crabtree-negative yeasts Candida utilis, Kluyveromyces marxianus and Hansenula polymorpha, growth in the presence of benzoate resulted in an increase in qO2 and, at high concentrations of benzoate, in aerobic fermentation. In contrast to S. cerevisiae, the highest qO2 of these yeasts when growing at D = 0.10 h-1 in the presence of benzoate was equal to, or lower than the qO2 attainable at mu(max) without benzoate. Enzyme activities that were repressed by glucose in S. cerevisiae also declined in K. marxianus when the glucose flux was increased by the presence of benzoate.(ABSTRACT TRUNCATED AT 400 WORDS)

1,326 citations

Journal ArticleDOI
Abstract: The ethanol yield and productivity obtained during fermentation of lignocellulosic hydrolysates is decreased due to the presence of inhibiting compounds, such as weak acids, furans and phenolic compounds formed or released during hydrolysis. This review describes the effect of various detoxification methods on the fermentability and chemical composition of the hydrolysates. Inhibition of fermentation can be relieved upon treatment with the ligninolytic enzyme laccase, pre-fermentation by the filamentous fungus Trichoderma reesei, removal of non-volatile compounds, extraction with ether or ethyl acetate, and treatment with alkali or sulfite. Various fermentation strategies can also be used to improve yield and productivity in lignocellulosic hydrolysates. Batch, fed-batch, and continuous fermentation are discussed in relation to inhibition of fermentation in lignocellulosic hydrolysates.

1,244 citations

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