Purpose -The aim of this study was to evaluate the influence of temperature and action time on the extraction rate of carbohydrates of Jerusalem artichoke concentrate powder and inactivation of inulin during boiling and sterilization. Design/methodology/approach -Water suspension of Jerusalem artichoke concentrate (5 g/ 100 ml) at 25, 50 and 100 C was tested after 5, 15, 30 and 60 min to determine the content of inulin, glucose, fructose and sucrose and evaluate the extraction rate. The stability of inulin was studied after boiling and sterilization at 120 C during 1, 2 and 3 h. The extraction rate was evaluated by Fourier-Transform Infrared (FT-IR) spectroscopy as well. Findings -It was shown that extraction of soluble carbohydrates -fructose, glucose, sucrose and inulin, from water suspension of Jerusalem artichoke concentrate was practically completed in 5 min at 25 C. The extraction rate was not significantly influenced by temperatures lower than 100 C. Inulin was stable during boiling for 1 h but sterilization for 1 h caused significant losses. Infrared spectral analysis of soluble and insoluble fractions showed that inulin was practically fully extracted. Originality/value -The paper shows that inulin can be easily extracted from Jerusalem artichoke concentrate powder even at 25 C and it maintains for 60 min at temperatures up to 100 C, nevertheless boiling or sterilization at higher temperatures for longer time causes significant loses of inulin and consequently the functional quality of Jerusalem artichoke powder. These results must be taken into account when applying inulin concentrates as functional food components.

The non-conventional yeast Kluyveromyces marxianus is an emerging industrial producer for many biotechnological processes. Here, we show the application of a biomass-linked stoichiometric model of central metabolism that is experimentally validated, and mass and charge balanced for assessing the carbon conversion efficiency of wild type and modified K. marxianus. Pairs of substrates (lactose, glucose, inulin, xylose) and products (ethanol, acetate, lactate, glycerol, ethyl acetate, succinate, glutamate, phenylethanol and phenylalanine) are examined by various modelling and optimisation methods. Our model reveals the organism's potential for industrial application and metabolic engineering. Modelling results imply that the aeration regime can be used as a tool to optimise product yield and flux distribution in K. marxianus. Also rebalancing NADH and NADPH utilisation can be used to improve the efficiency of substrate conversion. Xylose is identified as a biotechnologically promising substrate for K. marxianus.

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The current study evaluated a newer method, which includes a dehydration step, of immobilizing Saccharomyces cerevisiae L-77 and S. cerevisiae L-73 onto hydroxylapatite and chamotte ceramic supports. The efficiency of cell immobilization on chamotte was significantly higher than hydroxylapatite. Immobilized yeast preparations were investigated for their ethanol-producing capabilities. The glucose concentration in a fermentation medium was 100 mg/mL. Immobilized preparations produced the same amount of ethanol (48 ± 0.5 mg/mL) as free cells after 36 H of fermentation. During the early stages of fermentation, immobilized yeast cells produced ethanol at a higher rate than free cells. Yeast preparations immobilized on both supports (hydroxylapatite and chamotte) were successfully used in six sequential batch fermentations without any loss of activity. The chamotte support was more stable in the fermentation medium during these six cycles of ethanol production. In addition to the high level of ethanol produced by cells immobilized on chamotte, the stability of this support and its low cost make it a promising material for biotechnologies associated with ethanol production.

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