Direct Fermentation Of Starch Research Articles

Direct starch fermentation to L-lactic acid by a newly isolated thermophilic strain, Bacillus sp. MC-07.

A newly isolated Bacillus sp. MC-07 showed 99.2 % 16S rRNA gene sequence similarity with the Bacillus thermoamylovorans LMG 18084(T). It demonstrated optimum and maximum growth temperatures of 50 and 62 °C, respectively. The ability of MC-07 to produce optically pure L-lactic acid via direct fermentation of starch without enzymatic hydrolysis was investigated at different pH values (6.0-8.0) by intermittent adjustments every 12 h. During batch fermentation in mineral salt medium containing 0.001 % yeast extract at pH 7.0, 20 g/L of soluble starch was utilized to produce 16.6 g/L L-lactic acid at 50 °C within 24 h of fermentation, with 100 % optical purity, 92.1 % lactic acid selectivity, and an L-lactic acid yield of 0.977 g/g. Direct starch fermentation at pHs 6.0, 6.5, 7.5, and 8.0 resulted in considerably lower concentrations of lactic acid than did at pH 7.0. Compared with B. thermoamylovorans LMG 18084(T), the ability of strain MC-07 to produce L-lactic acid was superior.

Fermentation of glucose and starch particles using an inexpensive medium

AbstractBACKGROUND: In North America, compared with sugar, starch is a more economical raw material to produce ethanol. Recently low temperature processing of starch granules directly to ethanol has been commercialized. With a view to minimizing process costs while maintaining a satisfactory ethanol yield, an inexpensive medium that does not require the addition of commercial α‐amylase has been developed for low temperature, direct fermentation of starch particles.RESULTS: Compared with an expensive medium that contained both yeast extract and α‐amylase, the inexpensive medium resulted in identical and 10% higher ethanol yields using glucose and starch granules as the raw substrates, respectively, but required longer processing times. Based on the different ingredient prices for expensive and inexpensive media, the operating cost to produce 10 million litres per year of ethanol utilizing simultaneous raw starch hydrolysis and fermentation is reduced over $ 2 million (Cdn) per year when using inexpensive medium.CONCLUSION: The new inexpensive medium and simultaneous raw starch hydrolysis and fermentation is considered the best strategy to produce ethanol directly from starch particles in North America. Copyright © 2009 Society of Chemical Industry

Efficient and Direct Fermentation of Starch to Ethanol by Sake Yeast Strains Displaying Fungal Glucoamylases

Aspergillus oryzae glucoamylases encoded by glaA and glaB, and Rhizopus oryzae glucoamylase, were displayed on the cell surface of sake yeast Saccharomyces cerevisiae GRI-117-UK and laboratory yeast S. cerevisiae MT8-1. Among constructed transformants, GRI-117-UK/pUDGAA, displaying glaA glucoamylase, produced the most ethanol from liquefied starch, although MT8-1/pUDGAR, displaying R. oryzae glucoamylase, had the highest glucoamylase activity on its cell surface.

Dark Hydrogen Fermentation from Hydrolyzed Starch Treated with Recombinant Amylase Originating from Caldimonastaiwanensis On1

Starch is one of the most abundant resources on earth and is suited to serve as a cost-effective feedstock for biological hydrogen production. However, producing hydrogen from direct fermentation of starch is usually inefficient, as the starch hydrolysis is often the rate-limiting step. Therefore, in the present work, enzymatic starch hydrolysis was conducted to enhance the feasibility of using starch feedstock for H2 production. The amylase (with a molecular weight of ca. 112 kDa) used for starch hydrolysis was produced from a recombinant E. coli harboring an amylase gene originating from Caldimonas taiwanensis On1. Using statistical experimental design, the optimal pH and temperature for starch hydrolysis with the recombinant amylase was pH 6.86 and 52.4 degrees C, respectively, at an initial starch concentration of 7 g/L. The hydrolyzed products contained mainly glucose, maltotriose, and maltotetrose, while a tiny amount of maltose was also detected. The enzymatically hydrolyzed products of soluble starch and cassava starch were used as the substrate for dark hydrogen fermentation using Clostridium butyricum CGS2 and Clostridium pasteurianum CH4. The highest H2 production rate (vH2) and yield (YH2) of C. butyricum CGS2 was 124.0 mL/h/L and 6.32 mmol H2/g COD, respectively, both obtained with the hydrolysate of cassava starch. The best H2 production rate (63.0 mL/h/L) of C. pasteurianum CH4 occurred when using hydrolyzed cassava starch as the substrate, whereas the highest yield (9.95 mmol H2/g COD) was obtained with the hydrolyzed soluble starch.

Optimization of ethanol production from starch by an amylolytic nuclear petite Saccharomyces cerevisiae strain

Ethanol fermentation characteristics of the 100% respiratory-deficient nuclear petite amylolytic Saccharomyces cerevisiae NPB-G strain was investigated in both shake-flask and controlled bioreactor cultivation conditions, and comparison with the earlier reported results revealed 54.6% increase in ethanol yield. Efforts to improve the starch utilization rate by increasing the selection pressure or supplying the fermentation medium with glucose did not prevent the observed decrease in time-dependent amylolytic activity. Response surface methodology (RSM) was then used as a statistical tool to optimize the initial yeast extract and starch contents of the medium, which resulted in a substantial increase in the stability of the expression plasmid in both the respiratory-deficient NPB-G and the parental respiratory-sufficient WTPB-G strains, with concomitant improvement in their amylolytic potentials. High ethanol yields on substrate values of the bioreactor cultures, which were very close to the theoretical yield, indicated that the amylolytic respiratory-deficient NPB-G strain was effective in the direct fermentation of starch into ethanol.

Bioconversion of starch into ethanol by a recombinant Saccharomyces cerevisiae strain YPG-AB

The direct fermentation of starch into ethanol by a recombinant Saccharomyces cerevisiae strain YPG/AB, which expresses Bacillus subtilis α-amylase and Aspergillus awamori glucoamylase as separately secreted polypeptides, was investigated in both batch and fed-batch fermenter systems under controlled conditions. A 34% increase was observed in ethanol production by YPG/AB in a 40 g l −1 initial starch containing medium supplemented with 4 g l −1 glucose. Ethanol productivities were calculated as 0.35, 0.33 and 0.27 g l −1 h −1 for media with pH 4.5, 5.6 and 6.5, respectively. Substrate controlled fed-batch cultures were used to increase the ethanol production rate. The amount of ethanol produced in fed-batch culture (47.5 g l −1) increased by 200% compared to batch culture (15.6 g l −1). Starch fermentation by S. cerevisiae YPG-AB strain was characterized by ethanol yields/productivities higher than those obtained in comparable fermentations on starch reported in literature.

Substrate regulation and specificity of amylases fromAureobasidiumstrain NRRL Y-12,974

Pullulan is an industrial biopolymer produced by the yeast-like fungus Aureobasidium, usually by direct fermentation of starch. Despite evidence that autogenous amylases produced during these fermentations are detrimental to the final molecular mass of the product, fundamental studies of these enzymes have not been reported. Total extracellular amylases were studied from the promising production strain NRRL Y-12,974. Growth rates and yields were equivalent in cultures grown on glucose, maltose, soluble starch, or cornstarch. Total amylase levels were low and varied only three-fold, from 0.01 IU ml−1 in glucose-grown cultures to 0.03 IU ml−1 in soluble-starch-grown cultures. All cultures showed both α-amylase activity and activity against pullulan. Synthetic oligosaccharide substrates were apparently attacked by an α-glucosidase, produced in highest levels by maltose-grown cultures.