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This study aimed to select a yeast strain that effectively utilises xylose to produce xylitol from the vinasse of ethanol broth obtained from the fermentation of sugarcane bagasse hydrolysate. Eleven strains of xylose-fermenting yeasts were evaluated for their abilities to utilise xylose and produce xylitol. Two strains that showed outstanding performance in the semi-defined xylose medium were selected for further testing with a vinasse medium. Candida guilliermondii TISTR 5068 showed a superior xylitol production of 7.03 ± 0.08 g/L with the xylitol yield of 0.70 g/gxylose when cultured in bagasse-based ethanol vinasse. The strain was further tested for its xylitol production performance when cultured at four different agitation intensities. Excessive agitation resulted in a rapid xylitol production rate but caused xylitol consumption once the xylose was depleted. Moderate agitation resulted in the highest xylitol yield of 0.79 g/gxylose. The results of this study have provided important information for the development of the xylitol production process using waste streams from cellulosic ethanol production.

Microalgae are considered a third generation feedstock for biofuel production. Apart from lipid accumulation, some microalgae also accumulate carbohydrates which could be extracted and used as substrate for other biofuels production. This research aimed to assess potential of biomass of microalgae, Chlorella sp., for its potential as a feedstock for ethanol production. Response surface analysis was used to determine the conditions for pretreatment of microalgae biomass by acid-hydrothermal. The analysis suggested the use of 20% biomass in 1.5% sulfuric acid at 117 °C for 20 min as suitable for the pretreatment as it resulted in the maximum ethanol of 5.62 ± 0.16 g/L, which was 3.5 times higher compared with using untreated biomass. Enhanced ethanol production was investigated by hydrolyzing the pretreated slurry with α-amylase and glucoamylase. Using glucoamylase alone was enough for hydrolyzing the slurry to improve ethanol production. By using 25 Unit/galgae of glucoamylase, ethanol produced from the hydrolysate increased to 10.58 ± 0.34 g/L or 52.88 ± 1.69 mg/galgae. Enhancing ethanol production from Chlorella sp. biomass by hydrolyzing the acid-hydrothermal pretreated slurry with glucoamylase resulted in a total of 7.1 times increase in ethanol production from Chlorella sp. biomass as compared with the use of the biomass without any treatment.

The objective of this study was to determine the effect of supplementing Kluyveromyces marxianus CPY1, K. marxianus RSY5 and Pichia kudriavzevii YSY2 isolated from ruminal fluid of dairy cows on transfer of aflatoxin B1 (AFB1) from feed into aflatoxin M1 (AFM1) in milk, DMI, milk production and nutrient digestibility. Four multiparous Holsteins in mid-lactation were used in a 4 &times, 4 Latin square design trial consisting of 14 days in each experimental period for sample collection. Between each period, 14 clearance days prior to the next treatment were allowed to minimize carryover effects. In each treatment, subsequent supplementation of isolated yeast was compared, i.e., (1) control (without yeast supplementation), (2) K. marxianus CPY1 (K1Y), (3) K. marxianus RSY5 (K2Y) and (4) P. kudriavzevii YSY2 (PY). All diets contained 22.28 &micro, g of AFB1/kg. Treatments were individually fed at the rate of 2 g/day (1 &times, 109 CFU/g) of yeast biomass or corn meal in the control group. Concentrations of AFM1 in milk was reduced with yeast and averaged 1.54, 0.36, 0.43 and 0.51 &micro, g/L for control, K1Y, K2Y and PY, respectively (p &lt, 0.01). The transfer of AFB1 from feed into AFM1 in milk was higher in control compared with K1Y, K2Y and PY (7.26% vs. 1.18%, 1.44% and 1.69% respectively, p &lt, 0.01). Supplementation of yeast also improved DMI and milk compositions, but no differences were observed in nutrient digestibility or milk yield among treatments. Concentration and yield of milk protein, fat, lactose, solid-not-fat (SNF) and total solids were greater in cows fed yeast compared with the control (p &lt, 0.01). These results indicate that K. marxianus CPY1, RSY5 and P. kudriavzevii YSY2 shows promise as a dietary supplementation to detoxify AFB1 and improve DMI and yield of milk components.

Aims To obtain yeast and bacteria from ruminal fluids that possess aflatoxin B1 (AFB1 ) detoxifying ability for use in animal feed. Methods and results Sources of isolation were ruminal fluids of three nonfistulated dairy cows, fed diets containing cassava pulp, rice straw or distillery yeast sludge. The isolation was carried out to screen for the isolates that were active in both anaerobic and aerobic conditions. Three yeast and three bacteria isolates were selected. Up to 85% of AFB1 was detoxified by yeast isolates and up to 60% AFB1 reduction was evident by bacteria isolates. Two yeast isolates were identified as Kluyveromyces marxianus and one isolate as Pichia kudriavzevii. The three bacteria isolates were identified as Enterococcus faecium, Corynebacterium phoceense and C. vitaeruminis. All strains showed high biomass production when cultivated in medium with 80 g l-1 glucose. Conclusions The isolated yeast and bacteria with AFB1 detoxifying ability showed a good potential to be applied as an aflatoxin-detoxifying agent to ingredients used to feed dairy cattle. Significance and impact of the study The abilities of isolates to survive and be active in anaerobic and aerobic conditions rendered them to be active in cattle's rumen. Their biomass could be produced in bulk and used as feed supplement for aflatoxin detoxification in dairy cattle.

Dextranase is commonly used for eliminating dextran contamination in sugar factory. This research, dextranase from Aspergillus allahabadii X26, was produced, purified and characterized including on dextran hydrolysis. A. allahabadii X26 was cultured in a medium containing 1% dextran T2000 as a carbon source in 5-l fermenter aerobically at 30 °C and obtain 110 U/ml crude extracellular dextranase activity within 9 days of incubation. Extracellular dextranase could be purified by the 2 steps of ammonium sulfate precipitation and affinity chromatography using Sephacryl S-300 HR. This resulted in 6.5-fold and a 39.1% recovery yield obtaining 3009 U/mg mg protein. The purified enzyme exhibited 66 kDa on SDS-PAGE and was specified as a glycoprotein. The optimum pH and temperature for enzyme activity were 5.8 and 55 °C, respectively. The enzyme exhibited thermostability in the range of 20–50 °C and pH 5–9 over the incubation period of 1.5 h. The dextranase activity was enhanced by Co2+, Mn2+ and Ca2+, whereas most ions and reagents did not inhibit its activity. The enzyme only had specificity to the α(1 → 6) glycosidic bond of dextran. Partial sequences of the enzyme determined by an ESI mass spectrometer showed similarity toward dextranase GH49. This purified dextranase (0.2 U/ml) from A. allahabadii X26 could degrade high molecular weight dextran into fragments of 5–10 kDa and oligodextrans within 5 min. These A. allahabadii X26 dextranase properties indicated high potential for dextran elimination in sugar production process.

We assess oleaginous yeast strains from five genera to identify the strain suitable to use sugarcane bagasse as a feedstock for lipid production. Upon initial assessment in glucose or xylose media, five potential strains were chosen for further assessment in sugarcane bagasse hydrolysate. All strains exhibited improved growth and lipid production due to a buffering capacity of the hydrolysate, with R. glutinis showing the best lipid production. The yeast growth and lipid production were similar over the pH range between 5.5 and 7.5. It performed best at 30 °C. Using baffled flask at 200 rpm resulted in the highest cell dry weight of 40 g/L and 20 g/L of lipid, while using 100 rpm or normal flasks resulted in a much lower growth and lipid production. The results from this study suggest that sugarcane bagasse could be a raw material for microbial lipid production, providing the control criteria are suitable.

Ethanol is one of the widely used liquid biofuels in the world. The move from sugar-based production into the second-generation, lignocellulosic-based production has been of interest due to an abundance of these non-edible raw materials. This study interested in the use of Napier grass (Pennisetum purpureum Schumach), a common fodder in tropical regions and is considered an energy crop, for ethanol production. In this study, we aim to evaluate the ethanol production potential from the grass and to suggest a production process based on the results obtained from the study. Pretreatments of the grass by alkali, dilute acid, and their combination prepared the grass for further hydrolysis by commercial cellulase (Cellic&reg, CTec2). Separate hydrolysis and fermentation (SHF), and simultaneous saccharification and fermentation (SSF) techniques were investigated in ethanol production using Saccharomyces cerevisiae and Scheffersomyces shehatae, a xylose-fermenting yeast. Pretreating 15% w/v Napier grass with 1.99 M NaOH at 95.7 &deg, C for 116 min was the best condition to prepare the grass for further enzymatic hydrolysis using the enzyme dosage of 40 Filter Paper Unit (FPU)/g for 117 h. Fermentation of enzymatic hydrolysate by S. cerevisiae via SHF resulted in the best ethanol production of 187.4 g/kg of Napier grass at 44.7 g/L ethanol concentration. The results indicated that Napier grass is a promising lignocellulosic raw material that could serve a fermentation with high ethanol concentration.