Stillage as a Source of Growth Promoting Biofactors and a Stimulator of Levan and Extracellular Levansucrase Synthesis for Zymomonas mobilis

In the present work, the fermentation of simultaneous production of ethanol and levan by Zymomonas mobilis grown on different growth media has been studied. Yeast extract, rye stillage or sugar beet molasses stillage were used as additives to the basic sucrose media and the chemical composition, including vitamins, of the cultivation liquids have been determined. It has been shown that 0.5 % of yeast extract dry weight additive could be substituted by 10.0 % of native stillage additive. It was established that molasses stillage stimulates the ethanol synthesis, but rye stillage additive is more preferable for levan production. The extracellular levansucrase obtained from the culture liquid …

Anhydrobiosis in yeasts: Psychrotolerant yeasts are highly resistant to dehydration.

Yeast cells are able to transition into a state of anhydrobiosis (temporary reversible suspension of metabolism) under conditions of desiccation. One of the most efficient approaches for understanding the mechanisms underlying resistance to dehydration-rehydration is to identify yeasts, which are stable under such treatments, and compare them with moderately resistant species and strains. In the current study, we investigated the resistance to dehydration-rehydration of six psychrotolerant yeast strains belonging to two species. All studied strains of Solicoccozyma terricola and Naganishia albida were found to be highly resistant to dehydration-rehydration. The viability of S. terricola str…

Levan-ethanol biosynthesis using Zymomonas mobilis cells immobilized by attachment and entrapment

Fermentation of sucrose by Zymomonas mobilis cells attached to stainless steel wire spheres (WS) and to Al2O3 granules was compared with sucrose fermentation by cells entrapped in Ca-alginate. Similar amounts of cell biomass were applied at the beginning of the immobilized fermentation systems. The immobilization of Z. mobilis cells to the carrier surface was checked by scanning electron microscopy (SEM). Most cells were present in holes and pores of Al2O3 surfaces following colonization. Observation of the carrier after repeated fermentation cycles showed that a surface of Al2O3 granules was partly covered by levan. Alginate beads were extended in volume and partly disrupted. Changing the …

2-Phenylethanol production by Kluyveromyces marxianus on glucose and lactose substrates

Catalytic treatment of rapeseed straw for enhanced production of furfural and glucose for bioethanol production

Abstract Ethanol produced from renewable biomass, such as lignocellulosic feedstock, is one of the most promising future biofuels. In this paper, rapeseed straw was tested as an abundant and cost-effective renewable resource material for the production of cellulosic glucose. Pre-treatment of this material is an important step to improve the efficiency of subsequent cellulose hydrolysis. In this study, we used two pre-treatment methods – hydrothermochemical and ultrasound. Studies have shown that, in the initial hydrothermal pre-treatment of rapeseed straw, Al2(SO4)3 may be used as an efficient catalyst, at least in procedures for obtaining glucose. An increase in the amount of this catalyst…

Fermentation of Jerusalem artichoke by Zymomonas and Saccharomyces

PurposeThe aim of this study is to find out the appropriate fermentation conditions of Jerusalem artichoke powder (JAP) based media to obtain light beverage containing inulin.Design/methodology/approachJAP water suspension or filtrate were used for preparation of growth media with or without enzymatic hydrolysis of inulin for fermentation by Zymomonas mobilis 113 “S” or Saccharomyces cerevisiae.FindingsIf enzymatic hydrolysis of inulin was not used significantly higher amount of inulin (7.42 per cent) was unconverted by Z. mobilis than by S. cerevisiae (2.22 per cent) while the ethanol concentration was much higher (2.86 per cent) after S. cerevisiae fermentation than after Z. mobilis ferme…

Effects of yeast immobilization on bioethanol production

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 pre…

Buckwheat based substrate fermentation - possibilities for non-traditional alcoholic beverage production

Sugar beet diffusion juice and syrup as media for ethanol and levan production byZymomonas mobilis

Abstract Sugar beet is an important crop cultivated widely in Europe. Roots contain up to 6–9 t/ha of fermentable sugar. Our laboratory is targeting to investigate the production possibilities of ethanol and levan by Zymomonas mobilis bacteria, using sugar beet juice or their syrup as raw material. The Z.mobilis strain 113 “S”;, selected in our institute, produces simultaneously with ethanol up to 40–70 g/1 fructose polymer levan in sucrose medium. It was established that Z.mobilis can convert sucrose into ethanol and levan in batch fermentation using natural sugar beet diffusion juice, without additives of mineral salts and growth factors. Syrup obtained in sugar industrial production by c…

Model-based biotechnological potential analysis of Kluyveromyces marxianus central metabolism

Abstract 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 engi…