Water activity: a possible external regulator in biotechnical processes

Hahn‐Hägerdal, Bärbel

doi:10.1016/0141-0229(86)90129-8

Cited by 97 publications

(30 citation statements)

References 57 publications

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“…The requirement of water for growth and metabolic activities of microorganisms and the consequent potential of the water activity of the medium in controlling fermentation processes are well established (Hahn-Hägerdal 1986). SSF is distinct from submerged fermentation (SmF) since microbial growth and product formation occur at or near the surface of the solid substrate particle having low moisture contents.…”

Section: Discussionmentioning

confidence: 99%

Optimization of fermentation conditions for cellulase production by Bacillus subtilis CY5 and Bacillus circulans TP3 isolated from fish gut

Ray¹

2007

Acta Ichthyol. Piscat.

144

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Section: Discussionmentioning

confidence: 99%

Optimization of fermentation conditions for cellulase production by Bacillus subtilis CY5 and Bacillus circulans TP3 isolated from fish gut

Ray¹

2007

Acta Ichthyol. Piscat.

144

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“…Often the environment of the immobilized cells, which is totally different from that of the suspended cells (e.g. reduced water activity, aw), is held to be responsible (Hahn-H~igerdal 1986). Diffusional limitations can also affect the physiological activity particularly of cells entrapped in a gel matrix Rehm 1986, 1988;Hannoun and Stephanopoulos 1986).…”

Section: Introductionmentioning

confidence: 99%

Comparison of fermentation properties and specific enzyme activities of free and calcium-alginate-entrapped Saccharomyces cerevisiae

Hilge-Rotmann

Rehm

1990

Appl Microbiol Biotechnol

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Physiological properties have been determined for calcium-alginate-entrapped Saccharomyces cerevisiae in comparison to cells in suspension under identical culture conditions. Cells grown in the form of microcolonies in the alginate beads showed faster glucose uptake and ethanol productivity with simultaneously decreased product and cell yields. Increased specific hexokinase and phosphofructokinase activities could be determined in these cells. Immobilized single cells showed only slightly enhanced glucose turnover and no higher specific hexokinase activity. The significant alterations in physiology are apparently connected with growth of the cells in aggregates.

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“…A simplified, more practical definition of water activity is the ratio of the equilibrium water vapor pressure (P) over a material to that over "pure" water (P 0 ) [16,17]:…”

Section: Resultsmentioning

confidence: 99%

Assessment of Xylanase Activity in Dry Storage as a Potential Method of Reducing Feedstock Cost

Smith

Thompson

et al. 2008

Appl Biochem Biotechnol

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Enzymatic preprocessing of lignocellulosic biomass in dry storage systems has the potential to improve feedstock characteristics and lower ethanol production costs. To assess the potential for endoxylanase activity at low water contents, endoxylanase activity was tested using a refined wheat arabinoxylan substrate and three commercial endoxylanases over the water activity range 0.21-1.0, corresponding to water contents of 5% to >60% (dry basis). Homogeneously mixed dry samples were prepared at a fixed enzyme to substrate ratio and incubated in chambers at a variety of fixed water activities. Replicates were sacrificed periodically, and endoxylanase activity was quantified as an increase in reducing sugar relative to desiccant-stored controls. Endoxylanase activity was observed at water activities over 0.91 in all enzyme preparations in less than 4 days and at a water activity of 0.59 in less than 1 week in two preparations. Endoxylanase activity after storage was confirmed for selected desiccant-stored controls by incubation at 100% relative humidity. Water content to water activity relationships were determined for three lignocellulosic substrates, and results indicate that two endoxylanase preparations retained limited activity as low as 7% to 13% water content (dry basis), which is well within the range of water contents representative of dry biomass storage. Future work will examine the effects of endoxylanase activity toward substrates such as corn stover, wheat straw, and switchgrass in low water content environments.

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Water activity: a possible external regulator in biotechnical processes

Cited by 97 publications

References 57 publications

Optimization of fermentation conditions for cellulase production by Bacillus subtilis CY5 and Bacillus circulans TP3 isolated from fish gut

Optimization of fermentation conditions for cellulase production by Bacillus subtilis CY5 and Bacillus circulans TP3 isolated from fish gut

Comparison of fermentation properties and specific enzyme activities of free and calcium-alginate-entrapped Saccharomyces cerevisiae

Assessment of Xylanase Activity in Dry Storage as a Potential Method of Reducing Feedstock Cost

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