Amylolytic Microorganisms Research Articles

Lactic acid bacteria and yeasts associated with spontaneous fermentations during the production of sour cassava starch in Brazil

Sour cassava starch is a traditional fermented food used in the preparation of fried foods and baked goods such as traditional cheese breads in Brazil. Thirty samples of sour cassava starch were collected from two factories in the state of Minas Gerais. The samples were examined for the presence of lactic acid bacteria, yeasts, mesophilic microorganisms, Bacillus cereus and faecal coliforms. Lactic acid bacteria and yeasts isolates were identified by biochemical tests, and the identities were confirmed by molecular methods. Lactobacillus plantarum and Lactobacillus fermentum were the prevalent lactic acid bacteria in product from both factories, at numbers between 6.0 and 9.0 log cfu g − 1. Lactobacillus perolans and Lactobacillus brevis were minor fractions of the population. Galactomyces geothricum and Issatchenkia sp. were the prevalent yeasts at numbers of 5.0 log cfu g − 1. A species similar to Candida ethanolica was frequently isolated from one factory. Mesophilic bacteria and amylolytic microorganisms were recovered in high numbers at all stages of the fermentation. B. cereus was found at low numbers in product at both factories. The spontaneous fermentations associated with the production of sour cassava starch involve a few species of lactic acid bacteria at high numbers and a variety of yeasts at relatively low numbers.

Use of starch and potato peel waste for perchlorate bioreduction in water

The cost of carbon substrates for microbial reduction of perchlorate (ClO 4 −) is central to the success and competitiveness of a sustainable bioremediation strategy for ClO 4 −. This study explored the potential application of starch in combination with an amylolytic bacterial consortia and potato peel waste for ClO 4 − bioreduction. We obtained a potent amylolytic bacterial consortium that consisted of a Citrobacter sp . S4, Streptomyces sp. S2, Flavobacterium sp. S6, Pseudoxanthomonas sp. S5, Streptomyces sp. S7, and an Aeromonas sp. S8 identified by 16S rDNA sequencing. ClO 4 − concentration substantially decreased in purified starch medium inoculated with the amylolytic bacterial consortium and Dechlorosoma sp. perclace. Potato peel waste supported ClO 4 − reduction by perclace with the rate of ClO 4 − reduction being dependent on the amount of potato peels. Over 90% ClO 4 − removal was achieved in 4 days in a single time point experiment with 2% (w/v) potato peels waste. ClO 4 − reduction in a non-sterile 0.5% potato peel media inoculated with perclace occurred with an initial concentration of 10.14±0.04 mg L −1 to 2.87±0.4 mg L −1 (71.7% reduction) within 5 days. ClO 4 − was not detected in the cultures in 6 days. In a non-sterile 0.5% potato media without perclace, ClO 4 − depletion occurred slowly from an initial value of 9.99±0.15 mg L −1 to 6.33±0.43 mg L −1 (36.63% reduction) in 5 days. Thereafter, ClO 4 − was rapidly degraded achieving 77.1% reduction in 7 days and not detected in 9 days. No susbstantial reduction of ClO 4 − was observed in the sterile potato peel media without perclace in 7 days. Redox potential of the potato peel cultures was favorable for ClO 4 − reduction, decreasing to as low as −294 mV in 24 h. Sugar levels remained very low in cultures effectively reducing ClO 4 − and was substantially higher in sterilized controls. Our results indicate that potato peel waste in combination with amylolytic microorganisms and Dechlorosoma sp. perclace can be economically used to achieve complete ClO 4 − removal from water.

Biochemical characterization of α-amylase from the yeast Cryptococcus flavus

During our screening of amylolytic microorganisms from Brazilian fruits, we isolated a yeast strain classified as Cryptococcus flavus. When grown on starch-containing medium this strain exhibited the highest amylase production after 24 h of cultivation. The extracellular amylase from C. flavus was purified from the culture broth by a single step using chromatography on a Sephacryl S-100 column. The enzyme was purified 16.14-fold with a yield of 50.21% of the total activity. The purified enzyme was a glycoprotein with an apparent molecular mass of 75 and 84.5 kDa as estimated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and gel filtration, respectively. The enzyme lost approximately 50% of the molecular mass after treatment with glycosidases. The major end products of starch, amylose, amylopectin, pullulan and glycogen were maltose and maltotriose. The K m value for the pure enzyme was 0.056 mg ml −1 with soluble starch as the substrate. Enzyme activity was optimal at pH 5.5 and 50°C. The enzyme retained 90% of the activity after incubation at 50°C for 60 min and was inhibited by Cu 2+, Fe 2+ and Hg 2+.

A rapid plate culture method for screening of amylase producing micro-organisms

A simple and rapid method is described for the detection of amylase-producing micro-organisms on solid media using Remazol Brilliant Blue-starch as substrate. The blue starch is incorporated into nutrient agar and amylase production is detected by the disappearance of the colour around the colonies. The method which is non-destructive, allows for direct visualization and isolation of amylolytic micro-organisms from the environment without prior replication of colonies.

Saccharification and alcohol fermentation in starch solution of steam-exploded potato.

Steam explosion pretreatment of potato for the efficient production of alcohol was experimentally studied. The amount of water-soluble starch increased with the increase of steam pressure, but the amounts of methanol-soluble material and Klason lignin remained insignificant, regardless of steam pressure. The potatoes exploded at high pressure were hydrolyzed into a low molecular liquid starch, and then easily converted into ethanol by simultaneous saccharification and fermentation using mixed microorganisms: an amylolytic microorganism, Aspergillus awamori, and a fermentation microorganism, Saccharomyces cerevisiae. The maximal ethanol concentration was 4.2 g/L in a batch culture at 15 g/L starch concentration, and 3.6 g/L in a continuous culture fed the same starch concentration. In the fed-batch culture, the maximal ethanol concentration increased more than twofold, compared to the batch culture.

Alcohol fermentation of starch by a genetic recombinant yeast having glucoamylase activity

Alcohol fermentation of starch was investigated using a direct starch fermenting yeast, Saccharomyces cerevisiae SR93, constructed by integrating a glucoamylase-producing gene (STA1) into the chromosome of Saccharomyces cerevisiae SH1089. The glucoamylase was constitutively produced by the recombinant yeast. The ethanol concentration produced by the recombinant yeast was 14.3 g/L which was about 1.5-fold higher than by the conventional mixed culture using an amylolytic microorganism and a fermenting microorganism. About 60% of the starch was converted into ethanol by the recombinant yeast, and the ethanol yield reached its maximum value of 0.48 at the initial starch concentration of 50 g/L. The fed-batch culture, which maintains the starch concentration in the range of 30 to 50 g/L, was used to produce a large amount of ethanol from starch. The amount of ethanol produced in the fed-batch culture increased about 20% compared to the batch culture. (c) 1997 John Wiley & Sons, Inc.

Effect of gamma-hexachlorocyclohexane on amylolytic microorganisms of soil and amylase activity.

Effect of gamma-hexachlorocyclohexane on amylolytic microorganisms of soil and amylase activity.

Ethanol production from starch by a coimmobilized mixed culture system of Aspergillus awamori and Saccharomyces cerevisiae

The development of a coimmobilized mixed culture sys tem of aerobic and facultative anaerobic microorganisms in Ca-alginate gel beads and the production of useful metabolites by the system were investigated. A coimmobilized mixed culture system of Aspergillus awamori (obligate aerobe) and Saccharomyces cerevisiae (facultative anaerobe) in Ca-alginate gel beads was used as a model system, and ethanol production from starch by the system was used as a model production. Mold Asp. awamori is an amylolytic microorganism while yeast S. cerevisiae is an ethanol producer. The two microorganisms grew competitively in the oxygen-rich surface area of the gel beads because they had similar oxygen demands in aerobic culture conditions. Neither microorganism exhibited "habitat segregation" in the gel beads and leaked yeast cells grew aerobically without ethanol production in the broth. Ethanol productivity was low under these conditions.A more desirable coimmobilized mixed culture system of Asp. awamori and S. cerevisiae was established by adding Vantocil IB (a biocidal compound) to the production medium. The antimicrobial activity of Vantocil IB was more effective with S. cerevisiae than with Asp. awamori, so that a dense mycelial layer of Asp. awamori formed in the surface of the gel beads While S. cerevisiae grew densely in the more inner areas of the gel beads. Also, yeast cell leakace was repressed and ethanol productivity was improved. The system with Vantocil IB produced ethanol of 4.5 and 12.3 g/L from 16 and 40 g/L starch, respectively. A continuous culture using this system with Vantocil IB was also carried out, and a stable steady state could be maintained for six days without leakage of yeast cells and contamination. The selection of a factor suitable for producing "habitat segregation" enabled the development of a coimmobilized mixed culture system of an aerobe and a facultative anaerobe. In this study, total habitat segregation was used to denote a tendency to exhibit denser growth in different parts of one gel bead.

Microfungus-yeast mixed cultures in the degradation of amylaceous wastes. I: Interactions affecting amylolytic activity

Some possible criteria in selection of amylolytic microorganisms for their mixed culture with non-amylolytic yeasts are discussed, and the growth of several microfungus-yeast mixed cultures on mussel processing wastes are studied.

Ethanol production from starch by a coimmobilized mixed culture system of Aspergillus awamori and Zymomonas mobilis

The production of ethanol from starch by a coimmobilized mixed culture system of aerobic and anaerobic microorganisms in Ca-alginate gel beads was investigated. The mold Aspergillus awamori was used as an aerobic amylolytic microorganism and an anaerobic bacterium, Zymomonas mobilis, as an ethanol producer. By controlling the mixing ratio of the microorganisms in the inoculum size, a desirable coimmobilized mixed culture system, in which the aerobic mycelia grew on and near the oxygen-rich surface of the gel beads while the anaerobic bacterial cells mainly grew in the oxygen-deficient central part of the gel beads, was naturally established under the aerobic culture conditions, and ethanol could be directly produced from starch by the system. The ethanol productivity by the system in flask culture was particularly affected by the shear stress (dependent on the shaking speed) which controlled the mycelial growth on the surface of the gel beads. Under optimum culture conditions in the flask culture, the glucose produced was instantly consumed, and was not observed in the culture broth; the final concentration of ethanol produced from 100 g/L starch was 25 g/L and the yield coefficient for ethanol, Y(pls), was 0.38. The ethanol productivity by the coimmobilized mixed culture system was compared with those by other various culture systems and the advantages of the system were clarified.

Production of lipid from starch by a nitrogen-controlled mixed culture of Saccharomycopsis fibuliger and Rhodosporidium toruloides

Production of lipid from starch in a two-component mixed culture in a fed batch process was studied. Saccharomycopsis fibuliger was used as the amylolytic microorganism and Rhodosporidium toruloides, which does not grow on starch, as the lipid producer. The concentration of nitrogen can be used as an external regulator of growth and competition in this process. The total biomass concentration decreased and the relative amount of Rh. toruloides increased with decreasing initial concentration of nitrogen in the medium. The highest lipid concentration (9.7 g·l-1), highest overall lipid production rate (0.15 g·l-1·h-1) and highest concentration of lipid in biomass (36.5%) were obtained in cultures with an initial nitrogen concentration of 0.5 g·l-1. Compared to monocultures of Lipomyces starkeyi and Aspergillus oryzae on starch, the mixed culture showed slightly lower conversion of starch to lipid but was superior in the final lipid concentration and the overall lipid production rate.

EFFECT OF FOLIAR TREATMENT OF VEGETATIVE PLANTS ON SOIL MICROBIAL FLORA

The article contains materials of scientific research reflecting the positive effect on the soil microflora of foliar treatment of vegetative plants with various preparations. A small-scale experiment on growing carrots on low-lying peat soil of the Yakhroma floodplain (Moscow region) was carried out. For foliar treatments were applied biological means, developed at VNIIMZ – biological product LPB (the active principle – agronomically useful microflora) and biological means BoHum (the active principle – humic substances). Spraying was carried out three times per season at a rate of flow of a working solution of 300 l / ha (dilution 1: 100, 1: 300, 1: 500). To assess the effect of biological means on soil processes in soil samples, the number of ammonifying, amylolytic and phosphate-mobilizing microorganisms was determined. The intensity of the mineralization processes in the soil was estimated from the value of the mineralization coefficient. It was established that the foliar treatment of vegetative plants carrot with biological means of LPB and BoHum increased the total number of identified soil microorganisms by 21-22%, while the mineralization of nitrogenous compounds in the soil during spraying with humic bio means occurred more intensively 3 times, and the biologic preparation of LPB 2.3 times, concerning the control. Activation of soil-microbiological processes (due to bio means entering the soil), together with the activation of physiological processes of plant growth and development (as a result of contact with bio means on the leaf plate of plants) increased carrot yield by 19.4 and 18.3%, respectively, when using LPB and BoHum in 1: 300 dilutions. The regression analysis data confirmed a statistically significant relationship between carrot yield and the total number of soil microorganisms (r = 0.67) and soil mineralization coefficient (r = 0.77). The positive effect of foliar treatments on the soil microflora was also revealed in the cultivation of spring wheat and potatoes.