Fermentation at high temperature with application of thermotolerant microorganisms is a technological advantage in bioethanol production. Among the yeasts, K. marxianus has outstanding thermotolarance. The industrial application of the IMB3 strain occurs usually at 45C. The final aim of our project is the genetic modification of the K. marxianu...s CBS712 strain in order to achieve ethanol production at higher temperature than the currently applied. This requires the characterization of the CBS712 strain, with special attention to the determination of the temperature limit of its growth and the amount of the ethanol produced. The temperature limit of growth was 48C in YPD medium. Elevation of the temperature above 45C led to an exponential drop of the cell viability. Ethanol production was tested in shaking flasks, in MYFM medium, under oxigene limited conditions, applying variable concentrations of glucose (12–20%) and different temperatures (45–47 ºC). Preliminary results have revealed that the elevation of glucose concentration increased the amount of ethanol produced. The amount of ethanol (appr. 5%)+ produced at the highest glucose concentration was not different at the tested temperatures (45, 46 and 47 ºC). The observation indicates the potential in raising the thermotolerance of the strain.
Bioenergies (among them e.g. bioalcohol) can be solutions for the replacement of fossil fuels. For its production, plants with high sugar or starch content can be used. Juice pressed from the stalk of sugar sorghum has high sugar content (14-17%) that makes it suitable for bioethanol production. During our experiment, we examined 53 restorer ma...le lines; among them 22 were silo type sugar sorghum. We studied the following traits: plant height, breeding time, level of foliation, stalk diameter, characteristics of stalk medulla, juice content of stalk, sugar content of stalk juice. According to examined characteristics, we selected six restorer male lines for studies in the forthcoming years: RL 1, RL 2, RL 3, RL 4, RL 5, RL 9, RL 12, RL 15, RL 18. Their stalk medullas were wet, stalk diameters were medium-thick, sugar contents of juices varied between 17 and 24% at the end of milk mature. Harvest was made in September, they can be classified into early maturation group. Male sterile female lines were the following: SL 1, SL 2, SL 3, SL 4, SL 5. The maintainer male lines were: CL 1, CL 2, CL 3, CL 4, CL 5. In Hungary, there are only a few male sterile female
lines, so we will use these lines for hybrid production during the next years.
Sweet sorghum can be utilized for bioethanol production because it has high sugar content (14-17%). We determined the most important nutritional values of 5 silo type sorghum lines in waxy and full maturation. The examined restorer lines were: RL 4, RL 9, RL 15, RL 18, K 1. The following nutritional parameters were examined: dry material conten...t, refractometric total sugar content, reducing sugar content. In waxy maturation 73.85-87.37% of dry matter in stalk juice makes the total sugar. Dry material content, total and reducing sugar content of stalk
decreases from waxy mature to full maturation.
There are differences between lines in dry matter (SzD5%=0.76), total sugar (SzD5%=0.79), reducing sugar content (SzD5%=0.30). RL 4 performed a decrease in total sugar content from 10.07% to 10.02% during this period, reducing sugar also decreased from 4.01% to 2.47%. RL 9 performed a decrease in total sugar content from 11.76% to 11.08% during this period. Reducing sugar also decreased from 3.17% to 2.01% in the waxy
maturation. RL 15 showed a total sugar content decrease from 15.43 % to 15.36%. The reducing sugar also decreased from 3.23% to 1.71% in waxy maturation. In RL 18 total mean sugar content during waxy maturation was 13.78% which dropped to 13.26% approaching full maturation. Reducing sugar also decreased from 4.11% to 2.23% in waxy mature. K 1 performed a decrease in total sugar content from 9.35% to 6.15% during this period, while reducing sugar also decreased from 1.52% to 0.77%.
These lines upcoming for experiments are perspectives since having excellent stalk juice nutritional parameters they are of great or very great height and their stalks are thick-very thick, stalk medullas are wet.
The ethanol production of the Kluyveromyces marxianus CBS712 strain was investigated among different kind of condition. We defined the conversion rate in order to know the efficiency of the ethanol production. To determine this value, it is crucial to characterize the residual glucose concentracio. We chose two method to determine the amount of... residual glucose. The first method is the thin layer chromatography (TLC) and the second method is the method of the glucose-oxidase enzyme. We found that the TLC method is reliable than the other method. The conversion rates were determined from these values and the ethanol values. The maximal ethanol production of the characterized Kluyveromyces marxianus CBS712 strain (5.6% (v/v) ethanol at 45 °C, 55.3% conversion rate) is comparable to those strains which are applied in industrial ethanol production nowadays.
Due to climatic barriers, the genetic variability of Sorghum varieties decreases away from the gene centre, therefore hybrids cultivated in Hungary are restricted to a relatively limited genetic basis. This limited genetic basis results in a lower rate of genetic improvement, so the genetic basis of cytoplasm factors are to be extended. We enha...nced the diversity of primary materials by fast neutron treatment. As a result of this treatment we detected sterile, deformed specimens with double panicles in the stock treated with a dose of 12.5 Gy in the M1 generation. Agronomically useful
specimens were found in the stock treated with 10 Gy and 7.5 Gy doses, where the leaf area index (LAI) and Harvest- index gave higher values than those of the control group. In the stock treated with 5 Gy dose, variations were less significant. In the reseeded M2 generation we detected albino specimens with extreme chlorophyll defects in the 10 Gy Zádor stock.