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1

Using respiratory deficient mutants of Saccharomyces cerevisiae to glucose and xylose cofermentation with Pichia stipitis

100%

Kordowska-Wiatr M. , Targonski Z.

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1997

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nr 4

94-102

EN

One of the main problems limiting the economic production of ethanol from lignocellulosic biomass is D-xylose fermentation. In a medium containing glucose and xylose, it is preferable to achieve conversion with glucose fermenting yeast like S. cerevisiae and xylose fermenting yeast like P. stipitis. In order to resolve this problem, it is better to use respiratory deficient mutants. In this research, respiratory deficient mutant strains S. cerevisiae V30 and Ja(a) were obtained and their ability to ferment glucose in coculture with P. stipitis was investigated. A higher xylose conversion was observed in P. stipitis cultivation with these mutants because of better oxygen conditions than in the culture with native S. cerevisiae. A degree of assimilated xylose did not efficiently increased ethanol yields but on the other hand it increased the production of yeast biomass. Process considerations in relation to the fermentative performances using different strains combinations are discussed.

2

Studies on susceptibility of selected pretreated ligninocellulosic materials on enzymic hydrolysis

100%

Pielecki J. , Targonski Z.

Biotechnologia

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2001

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nr 1

153-160

EN

Studies described in this paper were conducted in order to determine the dependence between the conditions of ligninocellulosic substrate pretreatment and its suceptibility to enzymic hydrolysis. In view of this, a semi-empirical mathematical model was used to examine the process of enzymic hydrolysis of cellulose by assuming that this reaction proceeds as a sum of two first order reactions with different rates of reactions. The application of quasi-Newtonian equations allowed for the determination of percentage fractions of easily and non-easily hydrolised cellulose in the structures of pretreated substrates.

3

The utility of unconventional oxygenation of culture in simultaneousl production of inulinase and invertase by yeasts K. marxianus K-2

100%

Pielecki J. , Targonski Z.

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2003

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nr 1

234-243

EN

In this study, the apparatus for continuous controlling of dissolved oxygen concentration in the culture media was used. The automatic dosing of hydrogen peroxide (decomposed to oxygen and water) was possible, and a significant increase of extracellular enzymatic activity of inulinase (2,5-fold) and invertase (1,5-fold) were obtained in comparison with the traditional aeration. It also minimizes contamination, lowers the expenses on power consumption on aeration and mixing, reduces foaming and, consequently, high cost of antifoam emulsion and bacteriological filters.

4

Production of fungal and bacterial cellulase- free ?-1,4-xylanase in submerged cultivation

80%

Udeh K. O. , Wesolowska-Trojanowska M. , Janas Z. , Targonski Z.

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nr 4

117-134

EN

An interest in cellulase-free ?-1,4-xylanase production has markedly increased in recent years due to its bio-friendly applications in the pulp and food industry. In the presented paper, the synthesis and function of its regulatory control system in different organisms were highlighted. The influence of various cultivation conditions such as substrate availability, temperature, pH, inducers and agitation on the formation of xylanase in relation to other enzymes was also discussed. Strain modifications by mutation and gene technology, followed by cultivation to obtain a cellulase-free ?-1,4-xylanase were also presented. In addition, applications of xylanase for bleaching in the pulp industry, clarification of beer or juice, maceration of vegetables, improvement of bread quality, liberation of fibres from hemp and flax as well as improvement of animal feeds were mentioned.

5

Biotransformation of L-arabinose to arabitol by yeasts from genera Pichia and Candida

80%

Kordowska-Wiater M. , Targonski Z. , Jarosz A.

Biotechnologia

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2008

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nr 1

177-188

EN

Biotransformation of L-arabinose to arabitol by selected yeasts was described. P. stipitis CCY 39501, P. guilliermondii DSM 70052, C. shehatae 3504, C. shehatae ATCC 22984, C. pseudotropicalis IPF 65, C. parapsilosis DSM 70125 were investigated to produce L-arabitol. C. parapsilosis DSM 70125 was the best producer of arabitol that was detected in concentrations 10-14 gdm-3 in the medium. The highest yield (0,78 gg-1) and productivity (0,036 g(gxh)-1) were also obtained for this strain. The other quite good producers of arabitol were P. guilliermondii DSM 70052 and C. shehatae ATCC 22984 that produced poliol with yields 0,43 gg-1 and 0,50 gg-1, respectively, in optimal conditions. Rotation conditions of shaker on the level 150 rpm and temperature of incubation 28C were selected to be optimal for biotransformation by all yeasts.

6

Xylitol: metabolism, microbial production and perspective in polymer substrates utilization

80%

Udeh K. O. , Kordowska-Wiater M. , Targonski Z.

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1997

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nr 3

27-37

EN

This article reviews the current concepts in microbial production of xylitol with pure D-xylose or processed lignocellulosic materials as substrates by yeast strains such as Candida tropicals, C. guilliermondii and Debaromyces hansenii. The importance of xylitol as sugar substitute and coating agent in the production and preparation of food and pharmaceutical products was presented. In addition, the metabolism of D-xylose to xylitol, physiology of the yeast strains and biotechnological parameters affecting the formation of xylitol were discussed.