Kluyveromyces Sp Research Articles

Feasibility of ethanol production with enhanced sugar concentration in bagasse hydrolysate at high temperature using Kluyveromyces sp. IIPE453

Background: Ethanol from lignocellulosic biomass and nonfood sources has caught worldwide attention because of its potential use as an alternative automotive fuel. Results: In batch fermentation using Kluyveromyces sp. IIPE453 at 50°C on bagasse hydrolysate containing total fermenting sugar concentration 35 ±1.9 g l-1, the strain could produce ethanol concentration 14.5 ± 0.2 g l-1 with ethanol productivity 0.71 ± 0.001 g l-1 h-1 as compared with sugarcane juice 2 ± 0.04 g l-1 h-1, molasses 2.6 ± 0.05 g l-1 h-1 and mahua flower extract 3.4 ± 0.06 g l-1 h-1. In addition, the fermentation was carried out with enhanced sugar concentration in bagasse hydrolysate by mixing sugarcane juice, molasses and extract of mahua flowers. The ethanol productivities upon mixture of bagasse hydrolysate with sugarcane juice, molasses and extract of mahua flowers were 1.7 ± 0.06 g l-1 h-1, 1.75 ± 0.03 g l-1 h-1 and 2.57 ± 0.1 g l-1 h-1, respectively. Conclusion: The ethanol productivity could be increased by enhancing sugar concentration in bagasse hydrolysate. The product inhibition could be minimized by in situ ethanol recovery at high temperature.

Ethanol and xylitol production from glucose and xylose at high temperature by Kluyveromyces sp. IIPE453

A yeast strain Kluyveromyces sp. IIPE453 (MTCC 5314), isolated from soil samples collected from dumping sites of crushed sugarcane bagasse in Sugar Mill, showed growth and fermentation efficiency at high temperatures ranging from 45 degrees C to 50 degrees C. The yeast strain was able to use a wide range of substrates, such as glucose, xylose, mannose, galactose, arabinose, sucrose, and cellobiose, either for growth or fermentation to ethanol. The strain also showed xylitol production from xylose. In batch fermentation, the strain showed maximum ethanol concentration of 82 +/- 0.5 g l(-1) (10.4% v/v) on initial glucose concentration of 200 g l(-1), and ethanol concentration of 1.75 +/- 0.05 g l(-1) as well as xylitol concentration of 11.5 +/- 0.4 g l(-1) on initial xylose concentration of 20 g l(-1) at 50 degrees C. The strain was capable of simultaneously using glucose and xylose in a mixture of glucose concentration of 75 g l(-1) and xylose concentration of 25 g l(-1), achieving maximum ethanol concentration of 38 +/- 0.5 g l(-1) and xylitol concentration of 14.5 +/- 0.2 g l(-1) in batch fermentation. High stability of the strain was observed in a continuous fermentation by feeding the mixture of glucose concentration of 75 g l(-1) and xylose concentration of 25 g l(-1) by recycling the cells, achieving maximum ethanol concentration of 30.8 +/- 6.2 g l(-1) and xylitol concentration of 7.35 +/- 3.3 g l(-1) with ethanol productivity of 3.1 +/- 0.6 g l(-1) h(-1) and xylitol productivity of 0.75 +/- 0.35 g l(-1) h(-1), respectively.

Biological Interactions to Select Biocontrol Agents Against Toxigenic Strains of Aspergillus flavus and Fusarium verticillioides from Maize

Biological control represent an alternative to the use of pesticides in crop protection. A key to progress in biological control to protect maize against Fusarium verticillioides and Aspergillus flavus maize pathogens are, to select in vitro, the best agent to be applied in the field. The aim of this study was to examine the antagonistic activity of bacterial and yeast isolates against F.verticillioides and A. flavus toxigenic strains. The first study showed the impact of Bacillus amyloliquefaciens BA-S13, Microbacterium oleovorans DMS 16091, Enterobacter hormomaechei EM-562T, and Kluyveromyces spp. L14 and L16 isolates on mycelial growth of two strains of A. flavus MPVPA 2092, 2094 and three strains of F. verticillioides MPVPA 285, 289, and 294 on 3% maize meal extract agar at different water activities (0.99, 0.97, 0.95, and 0.93). From this first assay antagonistics isolates M. oleovorans, B. amyloliquefaciens and Kluyveromyces sp. (L16) produced an increase of lag phase of growth and decreased a growth rate of all fungal strains. These isolates were selected for futher studies. In vitro non-rhizospheric maize soil (centrally and sprayed inoculated) and in vitro maize (ears apex and base inoculated) were treated with antagonistics and pathogenic strains alone in co-inoculated cultures. Bacillus amyloliquefaciens significantly reduced F. verticillioides and A. flavus count in maize soil inoculated centrally. Kluyveromyces sp. L16 reduced F. verticillioides and A. flavus count in maize soil inoculated by spray. Kluyveromyces sp. L16 was the most effective treatment limiting percent infections by F. verticillioides on the maize ears.

Determination of the Optimum Conditions for Ethanol Production from Whey by Utilization the Local Isolate Kluyveromyces sp.

A series of experiments were conducted to explore the optimum conditions for ethanol production from cheese whey. The optimum conditions were: incubation period, 8 days, fermentation temperature, 30◦c, Size of inoculum, 1.15 x 106 C.F.U/ml, initial pH of medium, 5.0. The optimum composition of the fermentation medium were : Whey containing 9.3% lactose and fortified with ( NH4)SO4, 0.015 % , Yeast Extract, 0.01% , K2HPO4, 0.015% and it was found that the addition of date Syrup at a level of 0.5% noticeably increased ethanol yield compared with the medium which contain no date Syrup. By collective utilization of all the optimum conditions mentioned above, the following results were obtained, metabolized lactose 70.9%, ethanol production 4.48% and fermentation efficiency 132.36%.

Intergeneric protoplast fusion between Kluyveromyces and Saccharomyces cerevisiae - to produce sorbitol from Jerusalem artichokes

The construction of inulin-assimilating and sorbitol-producing fusants was achieved by intergeneric protoplast fusion between Kluyveromyces sp. Y-85 and Saccharomyces cerevisiae E-15. The cells of parental strains were pretreated with 0.1% EDTA (w/v) and 2-mercaptoethanol (0.1%, v/v) and then exposed to 2.0% (w/v) Zymolase at 30 °C for 30–40 min. The optimized fusion condition demonstrated that with the presence of 30% (w/v) polyethylene glycol 6000 (PEG-6000) and 10 mM CaCl2 for 30 min, the fusion frequency reached 2.64 fusants/106 parental cells. The fusants were screened by different characters between two parental strains and further identified by DNA contents, inulinase activity and sorbitol productivity. One of the genetically stable fusants, Strain F27, reached a maximal sorbitol production of 4.87 g/100 ml under optimal fermentation condition.

Continuous preparation of fructose syrups from Jerusalem artichoke tuber using immobilized intracellular inulinase from Kluyveromyces sp. Y-85

Partially purified intracellular inulinase from Kluyveromyces sp.Y-85 was immobilized covalently by adsorb-crosslinking onto a macroporus ionic polystyrene beads. Using a 4.5% (w/v) fructan solution from Jerusalem artichoke tuber as substrate, in a continuous bed column reactor packed with 70 ml of the immobilized inulinase beads, the maximum volumetric productivity of 234.9 g reducing sugars l −1 h −1 was obtained with fructan hydrolysis of 75%. The hydrolytic product was a mixture of 85% d-fructose and 15% d-glucose. The half-life of the bioreactor was estimated to be 32 days.

Isolation of a mutant of Kluyveromyces sp. Y-85 resistant to catabolite repression

The production of inulinase in Kluyveromyces sp. Y-85 is repressed by the carbon catabolites. To screen for derepression mutants, the strain of Kluyveromyces sp. Y-85 was treated with the mutagenic agent, ethyl methane sulfonate (EMS). Initially, mutants resistant to catabolite repression by 2-deoxy- d-glucose were isolated. One such mutant, Kluyveromyces sp. Y-85 K 6, was found to exhibit stable, 2-fold higher expression of inulinase than the wild-type in glucose-containing medium, indicating that it is a promising strain for industrial production.

Optimizing the culture conditions for higher inulinase production by Kluyveromyces sp. Y-85 and scaling-up fermentation

The response surface method (RSM) was used to optimize the medium for the production of inulinase by Kluyveromyces sp. Y-85. The inulinase production was adequately approximated with a full quadratic equation obtained from a four-factor-five-level central composite design. Analyses of the quadratic surfaces showed that in a 24-h fermentation at 30°C, the maximum inulinase activity 59.5 U/ml appeared at extract of Jerusalem artichoke, urea, beef extract, corn steep liquor concentrations 8.0%, 2.0%, 0.2% and 4.0%, respectively. We further investigated the fermentation in 15 l fermentor and scaling-up in 1000 l tower fermentor. The inulinase activity in the scaling-up was 68.9 U/ml, which was the highest production reported at present, indicating that Kluyveromyces sp. Y-85 was an excellent strain for industrial production.

Preparation and properties of β-galactosidase confined in cells of Kluyveromyces sp.

Lactase (β- d-galactosidase EC 3.2.1.23) was immobilized in yeast cells of the genus Kluyveromyces. Comparison of various solvents or polycations led to the selection of a chloroform-ethanol mixture for cell permeabilization. The lactase was confined inside the ghosts, with a minimum deactivation, by treatment with 0.4% glutaraldehyde. The combined procedure, permeabilization by chloroform-ethanol and confinement by glutaraldehyde, was applied to strain, K. lactis CBS 683, yielding a biocatalyst with an activity of 3.8 units ONP per milligram dry weight as calculated from V max. The biocatalyst could be stored in suspension at 4°C for 14 months with 20% deactivation. The K m, 4.2 m m, was comparable to the values published for the free enzyme, and the biocatalyst was found free of diffusion limitation for the hydrolysis of ONPG in the range of concentration from 0.3 to 50 m m. The pH activity profile showed a sharp optimum around pH 6.5; the storage stability in buffer at 35°C was very good for pH values above 6.1. The biocatalyst was used and recovered by centrifugation seven times without loss of activity, for the hydrolysis of 5% lactose solution in buffer at 30°C, with a conversion of about 80%.