Production of alcohol from sugar beet molasses without heat or filter sterilization

Among three esters of p-hydroxybenzoate, n-butyl p-hydroxybenzoate was selected as the best antimicrobial substance. Molasses medium sterilized by this ester was used as a substrate for ethanol production. n-Butyl p-hydroxybenzoate (0.15% w/v) completely inhibited the growth of free yeast cell inoculum, Ca-alginate immobilized yeast inoculum and bacterial contaminants. Immobilization of the yeast cell inoculum in Ca-alginate with castor oil (6% v/v) offered a yeast cell protection against the inhibitory effect of n-butyl p-hydroxybenzoate. The presence of castor oil in this immobilization system did not affect the metabolic activity of the yeast in beads compared to the cells immobilized without castor oil. The yeast cell beads in this system completely utilized up to 25% molasses sugar with an ethanol yield of 10.58%, equal to 83% of its theoretical value. The beads were stable and could be used successfully for seven cycles of batch fermentation. The optimum fermentation temperature using this system was 35°C. Received 21 January 1997/ Accepted in revised form 05 May 1997     

Biosynthesis of invertase by Saccharomyces cerevisiae with sugarcane molasses as substrate

Biosynthesis of invertase by Saccharomyces cerevisiae 01K32 was inversely proportional to the concentration of sugarcane blackstrap molasses included in the medium. In a fermenter, an intracellular invertase activity of 440 U/g dry cells was obtained.     

Production of fructose and ethanol from sugar beet molasses using Saccharomyces cerevisiae ATCC 36858

The production of enriched fructose syrups and ethanol from beet molasses using Saccharomyces cerevisiae ATCC 36858 was studied. In batch experiments with a total sugar concentration between 94.9 and 312.4 g/L, the fructose yield was above 93% of the theoretical value. The ethanol yield and volumetric productivity in the beet molasses media with sugar concentration below 276.2 g/L were in the range of 59-76% of theoretical value and between 0.48 and 2.97 g of ethanol/(L x h), respectively. The fructose fraction in the carbohydrates content of the produced syrups was more than 95% when the total initial sugar concentration in the medium was below 242.0 g/L. Some oligosaccharides and glycerol were also produced in all tested media. Raffinose and the produced oligosaccharides were completely consumed by the end of the fermentation process when the total initial sugar concentration was below 190.1 g/L. The glycerol concentration was below 16.1 g/L. The results could be useful for a potential industrial production of ethanol and high-fructose syrup from sugar beet molasses.     

Drying trials and protein enrichment by microbial growth on cane and beet molasses distillery stillage

Summary It is well known that molasses stillage is difficult to dry because of its high hygroscopicity. This investigation was made to try to affect the drying capability of beet molasses stillage by the addition of gelling agents. Increase in crude protein and essential amino acid content of beet molasses was obtained by growing Brevibacterium flavum and Candida utilis. The results obtained showed that drying performance is probably due to an optimum combination of the chemico-physical properties of the raw material.     

Foaming in submerged citric acid fermentation on beet molasses

Summary Foam control is an important part of every fermentation technology. Chemical anti-foam agents (AFA) are surface active substances, which decrease the surface elasticity of liquids and prevent metastable foam formation. Most AFA must be mixed or dissolved in a suitable carrier substance if their antifoaming properties are to be fully utilized. The carrier seems to act as a reservoir from which the AFA is liberated.The toxicity of different AFA upon Aspergillus niger was tested in Petri dishes. Their effect on the decrease of the respiration ability of the test organism A. niger was tested in a Warburg apparatus. Various AFA were tested as pure substances, as emulsions in seed oil and as mixtures of different AFA in cylindrical vessels with sinter glass discs under similar conditions as in the fermentor. Using mentioned methods the most suitable AFA were tested in citric acid fermentation on beet molasses.Partly presented at the poster session of the meeting: Fungal Biotechnology, Glasgow, September 1978     

Pretreatment of beet molasses to increase pullulan production

Pretreatment of beet molasses with cation exchange resin, sulphuric acid, tricalcium phosphate, potassium ferrocyanide, and ethylenediaminetetraacetic acid and disodium salt (EDTA) to increase the production of pullulan was investigated. Among the above techniques used for the removal of heavy metals, sulphuric acid treatment gave better results regarding polysaccharide concentration, polysaccharide yield, and sugar utilization. Aureobasidium pullulans grown on beet molasses produced a mixture of pullulan and other polysaccharides. The pullulan content of the crude polysaccharide was 30–35%. The addition of nutrients improved the production of polysaccharide. A maximum polysaccharide concentration (32·0±1·0 g litre⁻¹) was achieved in molasses solution (70 g litre ¹ initial sugar concentration, pH 6·5–7·5) treated with sulphuric acid and supplemented with K₂HPO₄ 0·5%, -glutamic acid 1%, olive oil 2·5% and Tween 80 0·5%. In this case, the highest values of biomass dry weight (33·8±1·0 g litre⁻¹), polysaccharide yield (63·5±2·5%), and sugar utilization (97·5±1·5%) were obtained at pH 6·5, 3·5, and 4·5–7·5, respectively.     

Alcoholic Fermentation of beet molasses: study on stillage recycle

Summary Stillage recycle in beet molasses alcoholic fermentation can be lower the production costs by a decrease of energy requirements for waste water treatment but it becomes necessary to optimise, separately, the sugar and non sugar contents of the wort. It is shown that the increase of the wort osmolality, linked to stillage recycle disturbs yeast metabolism above 1,5 osmol. The observed inhibition which is dependent on both sugar and non sugar concentrations leads to an apparent link between yeast behaviour and the dry matter percent of the worts.     

Biotin vitamers content of lactose and beet molasses

The biotin activity of beet and lactose molasses against the test strain Saccharomyces cerevisiae 225 by auxanographic method was evaluated. The level of lactose molasses biotin activity is almost twice as high as that obtained in the case of beet molasses. The results of bioautography with test strains Saccharomyces cerevisiae 225 and Lactobacillus arabinosus 17-5 indicate the qualitative composition of biotin derivatives (vitamers) in both molasses. Depending on the various technological steps e.g. sterilization or clarification one may find differences in the content and qualitative composition of biotin vitamers.     

Inhibition of beet molasses alcoholic fermentation by lactobacilli

Summary Alcohol production rate decreases as the concentration of bacterial contaminants increases. In complex medium, such as beet molasses, an alternative mechanism can be used by homofermentative lactic bacteria (Lactobacillus casei). Lactic acid and associated products, especially acetic acid, are liberated into the medium. The inhibition induced by these metabolites was reinforced by the presence of viable lactobacilli. Offprint requests to: P. Villa     

The effects of nonvolatile toxic substances on the yeast growth during ethyl alcohol fermentations

Summary Nonvolatile toxins accumulated during alcohol fermentation reduce the yeast growth rate, but not the maximum cell concentration. Specific growth rates decline exponentially according to the increase in toxins. The accumulation of salts and proteins seem to be responsible for the inhibition.To whom all correspondence should be addressed.     

Effect of yeast extract concentration on growth ofSchizoccharomyces pombe

Summary The effect of yeast extract on the growth ofSchizosaccharomyces pombe was investigated using a complex-synthetic medium. Batch cultures at low-glucose concentration show that a too low concentration of yeast extract may limit the biomass formation. On this medium kinetics and yields were found to be similar to those obtained on a synthetic-defined medium under both aerobic and anaerobic conditions.     

Cysteine effects on yeast growth]

The effect of cysteine on yeasts with different requirements for exogenous pantothenic acid was studied during their cultivation in the synthetic nutrient medium. Cysteine added at a concentration of 4X10(-4) M and 6X10(-4) M inhibited the growth of Saccharomyces cerevisiae of the Krasnodarsk race and Candida utilis BKM y-74 to a great extent and that of Saccharomycodes ludwigii BKM y-1176 to a lesser extent. The inhibitory effect of cystein was reversed by pantothenic acid, beta-alanine, aspartate and aspartic acid. It is assumed that cysteine inhibits metabolic utilization of pantothenic acid.     

Batch fermentation kinetics of sugar beet molasses by Zymomonas mobilis

A new osmotolerant mutant strain of Zymomonas mobilis was successfully used for ethanol production from beet molasses. Addition of magnesium sulfate to hydrolyzed molasses allowed repeated growth without the need of yeast extract addition. The kinetics and yields parameters of fermentation on media with different molasses concentrations were calculated. The anabolic parameters (specific growth rate, mu, and biomass yield, Y(X/S)) were inhibited at elevated molasses concentrations while the catabolic parameters (specific ethanol productivity, q(p), and ethanol yield, Y(p/s)) were not significantly affected. In addition to ethanol and substrate inhibition, osmotic pressure effects can explain the observed results.     

Protection against cadmium toxicity in yeast by alcohol dehydrogenase.

A cDNA expression library from Schizosaccharomyces pombe was transformed into Saccharomyces cerevisiae to screen for genes capable of conferring cadmium resistance to S. cerevisiae cells. The cDNA library was cloned into the S. cerevisiae expression vector pDB20 which is designed to express cDNAs via the constitutively-expressed promoter of the gene for alcohol dehydrogenase I (ADH1). Terminator and polyadenylation signals are also provided by the ADH1 gene. Cadmium resistant colonies were shown to arise by a recombination event leading to the exchange of the S. pombe DNA with the chromosomal ADH1 gene and a consequent dramatic increase in the ADH1 gene expression due to the high copy number of the plasmid. The overexpression of ADH1 effectively buffered the cells for cadmium ions by formation of Cd-ADH.     

利用甜菜糖蜜补料发酵生产丁醇

从土壤中分离出1株适合利用甜菜糖蜜发酵生产丁醇的丙酮丁醇梭菌(Clostridium acetobutylicum)2N,通过优化发酵条件,得到最适发酵温度为33℃,玉米浆最适添加量为15g/L,发现甜菜糖蜜中还原糖质量浓度高于50g/L时影响菌株的生长和溶剂生产。以补料分批发酵方式降低底物抑制,33℃发酵48h后,丁醇和总溶剂的质量浓度分别达到14.15g/L和19.65g/L,丁醇质量分数超过70%。     

The effects of temperature on leaf growth of sugar beet varieties

Leaf growth of nine varieties of sugar beet (Beta vulgaris L.) was studied at constant temperatures of 7, 11, 15 and 20·C, using generalised logistic curves fitted to the data to estimate the parameters of growth. The rate of leaf appearance increased linearly with temperature and was the same in all varieties. There were differences between varieties in the weighted mean rates of expansion of leaf area per plant (ā), the temperature coefficient of ā and the leaf area duration (D); these differences were caused more by differences in rates of expansion and final sizes of individual leaves than by differences in rates of leaf production. The growth of the first six leaves produced by each plant was examined in detail. The greater size of successive leaves of plants and genotypic differences between comparable leaves were more attributable to differences in the rate than differences in the duration of leaf expansion. Increasing temperatures increased leaf size because they accelerated the rate of expansion more than they shortened the duration of the expansion phase. It is inferred that all effects arose through differences in the initial sizes of leaves before they unrolled from the shoot apex. Dry matter production was proportional to D but was partitioned more to the storage root at the colder temperatures. This may have been related to the differential effects of temperature on cell division and expansion and the relative contribution of these two processes to the final sizes of the leaves and storage root.     

The three zinc-containing alcohol dehydrogenases from baker's yeast,Saccharomyces cerevisiae

This review is a summary of our current knowledge of the structure, function and mechanism of action of the three zinc-containing alcohol dehydrogenases, YADH-1, YADH-2 and YADH-3, in baker's yeast, Saccharomyces cerevisiae. The opening section deals with the substrate specificity of the enzymes, covering the steady-state kinetic data for its most known substrates. In the following sections, the kinetic mechanism for this enzyme is reported, along with the values of all rate constants in the mechanism. The complete primary structures of the three isoenzymes of YADH are given, and the model of the 3D structure of the active site is presented. All known artificial mutations in the primary structure of the YADH are covered in full and described in detail. Further, the chemical mechanism of action for YADH is presented along with the complement of steady-state and ligand-binding data supporting this mechanism. Finally, the bio-organic chemistry of the hydride-transfer reactions catalyzed by the enzyme is covered: this chemistry explains the narrow substrate specificity and the enantioselectivity of the yeast enzyme.