Based on screening in flask fermentations performed in an anaerobic chamber, every feedstock (sugar beet, corn and glucose) was matched with appropriate Clostridium strain regarding to yield and productivity values. Sugar beet is a crop grown in the Czech Republic for the last 160 years which provides high yields and can be used in the non food field for the biofuel production. In fact, non-food utilization of sugar beet is already running in CR but only bioethanol is produced in this way in Agroethanol TTD. Regarding corn, its main portion is grown for cattle feeding in CR but at the same time, the size of cattle herds diminishes every year. As the important goals of the biofuels production are, beside others, also the support of farmers and maintenance of arable land areas, corn can be seen as an energetic crop, too. Glucose was taken as feedstock on assumption glucose cultivation medium can be seen as a very simple model of lignocellulosic material hydrolyzate the use of which is supposed in future.

A comparison of butanol production using corn, sugar beet juice and glucose together with relevant strains is provided in Table 1 and sugar beet seems to be the preferable option according to the presented parameters. It is also noteworthy to look at fermentation courses in all compared cases. Fermentation of corn by C. acetobutylicum was running with textbook­like biphasic behaviour, when at first acids were formed and in the second solventogenic phase coupled with sporulation a reutilization of acids occurred. However, both fermentation of sugar beet juice by Cbeijerinckii and fermentation of glucose by

C. pasteurianum differed from this "typical" course by start of butanol formation during exponential growth phase (both cases) and almost no reutilization of acids (C. pasteurianum).

Overall balances of mentioned fermentation courses can be expressed in form of equations (1-3). Similar expression of products in numbers has already been published (see Equation 4) by Jones & Woods (1986) where this equation reflected average results achieved with C. acetobutylicum and Cbeijerinckii strains published in literature till 1986. In the equations (1­4), C12H22O11, C6H12O6, C4H10O, C3H6O, C2H6O, C2H4O2, C4H8O2 stand for saccharose, glucose, butanol, acetone, ethanol, butyric acid and acetic acid, respectively.

Butanol production from saccharose by Cbeijerinckii:

1.00C12H22O11 ^ 1.22 C4H10O + 0.60C3H6O + 0.04C2H6O + 0.25C2H4O2 ( )

+ 0.20C4H8O2 + 1.60CO2 + 0.80H2 ( )

Butanol production from corn (expressed as glucose) by C. acetobutylicum:

1.0 C6H12O6 ^ 0.42 C4H10O + 0.21 C3H6O + 0.04 C2H6O

+ 0.12C2H4O2 + 0.06C4H8O2 + 0.58CO2 + 0.36H2

Butanol production from glucose by C. pasteurianum:

1.0 C6H12O6 ^ 0.54 C4H10O + 0.40 C3H6O + 0.02 C2H6O + 0.19C2H4O2 + 0.06C4H8O2 + 6.77CO2 + 3.98 H2

Butanol production (Jones & Woods 1986):

1.0 C6H12O6 ^ 0.56 C4H10O + 0.22 C3H6O + 0.07 C2H6O + 0.14 C2H4O2 ( )

+ 0.04 C4H8O2 + 2.21 CO2 + 1.35 H2 ( )

Ratio of 1-butanol per unit of sugar (hexose) was the highest for saccharose (0.61) and the lowest for starch (0.42) but it can be stated the results were similar as presented by Jones and Woods (1986). The only exception was case of C. pasteurianum, in which remarkable amounts of carbon dioxide and hydrogen were produced not only in acidogenesis but throughout the whole fermentation period. Other experiences with the mentioned raw materials and also possible alternation of expensive but usual cultivation medium supplements, yeast extract or yeast autolysate, with cheap waste product of milk industry, whey protein concentrate, is
presented in Patakova et al., (2009). Detailed description of the use of sugar beet juice as fermentation substrate for biobutanol production has been published, recently (Patakova et al., 2011b).