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Anasontzis G.E.,Chalmers University of Technology | Thuy N.T.,Food Industries Research Institute | Hang D.T.M.,Food Industries Research Institute | Huong H.T.,Food Industries Research Institute | And 4 more authors.
Biomass and Bioenergy | Year: 2017

With a production of 39 million metric tons each year, rice is one of the main agricultural products of Vietnam. Thus, rice straw is a significant by-product, whose use in a biorefinery process would contribute to the bio-based transformation of the Vietnamese and South East Asian economy. In order to find novel efficient enzyme mixtures for the hydrolysis of rice straw and other agricultural residues, we took advantage of the rapidly evolving biodiversity of Vietnam and screened 1100 new fungal isolates from soil and decaying plant tissues for their CMCase activity. We selected 36 strains and evaluated them for their cellulases, xylanases, and accessory enzymes activities. Most of these isolates belonged to the genera Aspergillus and Trichoderma. We identified a few promising isolates, such as A. brunneoviolaceus FEC 156, A. niger FEC 130 and FEC 705, and A. tubingensis FEC 98, FEC 110 and FEC 644, whose produced enzyme mixtures released a mass fraction of the sugar content of alkali-treated rice straw higher than 20%, compared to 10% for Trichoderma reesei RUT C-30. We verified that the black Aspergilli are particularly efficient in their saccharification ability. We also identified strains that although they produced low amounts of cellulases and xylanases, their enzyme mixtures had high saccharification efficiencies, indicating the importance of the synergy effect, rather than the amount of enzymes available. Our results highlight the intra-species variation, especially in the Trichoderma genus, regarding the biomass degradation characteristics and the associated range of enzymatic activities. © 2017 The Author(s)


PubMed | Food Industries Research Institute and Hanoi University of Science
Type: | Journal: International journal of food microbiology | Year: 2016

The roles of microorganisms in traditional alcoholic fermentation are often assumed based on abundance in the starter and activity in pure culture. There is a serious lack of hard evidence on the behavior and activity of individual microbial species during the actual fermentation process. In this study, microbial succession and metabolite changes during 7days of traditional Vietnamese alcoholic fermentation were monitored. Special attention was devoted to starch degradation. In total, 22 microbial species, including 6 species of filamentous fungi (Rhizopus microsporus, Rhizopus arrhizus, Mucor indicus, Mucor circinelloides, Cunninghamella elegans, Aspergillus niger), 1 yeast-like fungus (Saccharomycopsis fibuligera), 7 yeasts (Saccharomyces cerevisiae, Clavispora lusitaniae, Wickerhamomyces anomalus, Lindnera fabianii, Pichia kudriavzevii, Candida rugosa, Candida tropicalis), and 8 bacteria (Stenotrophomonas maltophilia, Lactobacillus brevis, Lactobacillus helveticus, Acinetobacter baumannii, Staphylococcus hominis, Bacillus megaterium, Enterobacter asburiae, Pediococcus pentosaceus) were identified. Despite the presence of a complex microbiota in the starter, the fermentation process is consistent and involves a limited number of functional species. Rapid change in microbial composition of fermentation mash was observed and it was correlated with ethanol content. Microbial biomass reached maximum during first 2days of solid state fermentation. Acidification of the medium took place in day 1, starch degradation in days 2, 3, 4, and alcohol accumulation from day 3. Although Sm. fibuligera dominated by cell count amongst potential starch degraders, zymography indicated that it did not produce amylase in the fermentation mash. In mixed culture with Rhizopus, amylase production by Sm. fibuligera is regulated by the moisture content of the substrate. Rhizopus was identified as the main starch degrader and S. cerevisiae as the main ethanol producer. Bacterial load was high but unstable in species composition and dominated by acid producers. M. indicus, Sm. fibuligera, W. anomalus and bacteria were regarded as satellite microorganisms. Their possible influence on organoleptic quality of fermentation product was discussed.


Thanh V.N.,Food Industries Research Institute | Thuy N.T.,Food Industries Research Institute | Chi N.T.,Food Industries Research Institute | Hien D.D.,Food Industries Research Institute | And 4 more authors.
International Journal of Food Microbiology | Year: 2016

The roles of microorganisms in traditional alcoholic fermentation are often assumed based on abundance in the starter and activity in pure culture. There is a serious lack of hard evidence on the behavior and activity of individual microbial species during the actual fermentation process. In this study, microbial succession and metabolite changes during 7 days of traditional Vietnamese alcoholic fermentation were monitored. Special attention was devoted to starch degradation. In total, 22 microbial species, including 6 species of filamentous fungi (Rhizopus microsporus, Rhizopus arrhizus, Mucor indicus, Mucor circinelloides, Cunninghamella elegans, Aspergillus niger), 1 yeast-like fungus (Saccharomycopsis fibuligera), 7 yeasts (Saccharomyces cerevisiae, Clavispora lusitaniae, Wickerhamomyces anomalus, Lindnera fabianii, Pichia kudriavzevii, Candida rugosa, Candida tropicalis), and 8 bacteria (Stenotrophomonas maltophilia, Lactobacillus brevis, Lactobacillus helveticus, Acinetobacter baumannii, Staphylococcus hominis, Bacillus megaterium, Enterobacter asburiae, Pediococcus pentosaceus) were identified. Despite the presence of a complex microbiota in the starter, the fermentation process is consistent and involves a limited number of functional species. Rapid change in microbial composition of fermentation mash was observed and it was correlated with ethanol content. Microbial biomass reached maximum during first 2 days of solid state fermentation. Acidification of the medium took place in day 1, starch degradation in days 2, 3, 4, and alcohol accumulation from day 3. Although Sm. fibuligera dominated by cell count amongst potential starch degraders, zymography indicated that it did not produce amylase in the fermentation mash. In mixed culture with Rhizopus, amylase production by Sm. fibuligera is regulated by the moisture content of the substrate. Rhizopus was identified as the main starch degrader and S. cerevisiae as the main ethanol producer. Bacterial load was high but unstable in species composition and dominated by acid producers. M. indicus, Sm. fibuligera, W. anomalus and bacteria were regarded as satellite microorganisms. Their possible influence on organoleptic quality of fermentation product was discussed. © 2016 Elsevier B.V.


Thanh V.N.,Food Industries Research Institute | Hai D.A.,Food Industries Research Institute | Hien D.D.,Food Industries Research Institute | Takashima M.,RIKEN | Lachance M.-A.,University of Western Ontario
International Journal of Systematic and Evolutionary Microbiology | Year: 2012

Thirteen strains of yeasts typical of the genus Moniliella were isolated from fermenting meat and meat processing tools in Vietnam. PCR fingerprints generated by primer (GAC)5 subdivided the strains into two distinctive genetic groups. In a phylogenetic tree based on D1/D2 large subunit rRNA gene sequences, the strains formed a well-supported clade with Moniliella spathulata and Moniliella suaveolens but represented two new lineages. The names Moniliella carnis sp. nov. and Moniliella dehoogii sp. nov. are proposed. The two novel species can be distinguished from each other and from known species of Moniliella based on phenotypic characteristics. It is assumed that the yeasts were associated with fatty substances that contaminated the meat processing tools. The type strain of Moniliella carnis is KFP 246T (= CBS 126447T = NRRL Y-48681T) and the type strain of Moniliella dehoogii is KFP 211T (= CBS 126564T = NRRL Y-48682T). © 2012 IUMS.


Thanh V.N.,Food Industries Research Institute | Hien D.D.,Food Industries Research Institute | Thom T.T.,Food Industries Research Institute
International Journal of Systematic and Evolutionary Microbiology | Year: 2013

Yeasts of the genus Moniliella were isolated from 651 flower samples collected in Vietnam, using an enrichment medium containing 50% glucose. Species of the genus Moniliella were found in 5% of the samples and 54 strains were isolated. The strains were identified based on D1/D2 LSU rRNA gene sequences as M. megachiliensis (15 strains), M. dehoogii (14 strains), and M. mellis (2 strains). The remaining 23 strains could not be reliably placed under any known species. Among them, 12 strains isolated from flowers of Ipomoea pes-caprae and Calotropis gigantea were peculiar for the intensive formation of chlamydospores. These strains could be subdivided into pigmented and non-pigmented groups. Both groups were identical in PCR fingerprints generated with primer (GAC)5 and in D1/D2 and ITS sequences. The yeast was closely related to M. fonsecae but differed from the latter by 52 nt (or 10.3% of divergence) in the D1/D2 sequence and 71 nt (or 16.9% of divergence) in the ITS sequence. The name Moniliella byzovii sp. nov. is proposed for this novel species. The type strain is TBY 2041.7T =CBS 12757T =NRRL Y-63661T. The MycoBank number is MB 803186. © 2013 IUMS.


Dat N.M.,Food Industries Research Institute | Hamanaka D.,Kyushu University | Tanaka F.,Kyushu University | Uchino T.,Kyushu University
Food Control | Year: 2010

In the dairy industry, processing surfaces contacting milk or milk residues at different pH values during washing and fermentation could change bacterial attachment behavior. In order to simulate and elucidate this process, stainless steel coupons were conditioned with skim milk at different pH values, and the influence of surface conditioning on bacterial adherence was investigated. When milk pH was decreased (by the addition of hydrochloric acid), milk proteins coagulated, and precipitates were made on stainless steel coupons. When milk pH was increased (by the addition of sodium hydroxide), little visible deposit was observed on the surfaces after conditioning. Obtained surfaces were then used to verify bacterial adherence by being exposed to a suspension of Lactobacillus paracasei subsp. paracasei NBRC 15889. The enumeration of adherent cells on these surfaces was carried out under a fluorescence microscope. After short contact with bacterial cells (30 min), surfaces which were previously conditioned with acidic milk, especially in pH from 3.8 to 5.5, had lower adherence in comparison with the control (untreated surface) and with basic milk samples. Conditioning at pH of 7.03 had the highest adherence in the tested pH range. Results also indicated that attachment increased with the exposure time. Very few bacterial cells appeared inside milk precipitates after 30 min of exposure. In contrast, many cells were observed to be present inside these precipitates after 12 h. To decrease bacterial adherence, surface conditioning with milk at low pH is recommended when bacterial contact is brief. Long periods of bacterial exposure are not advisable for any conditioning case. © 2010 Elsevier Ltd.


Dat N.M.,Food Industries Research Institute | Hamanaka D.,Kyushu University | Tanaka F.,Kyushu University | Uchino T.,Kyushu University
Food Control | Year: 2012

Microbial biofilms present in dairy farms may contaminate milk during milk harvest and transfer diseases from the environment to cows. In order to reduce biofilm formation with respect to the role of pH, a study involving the control of milk pH during long-term biofilm formation of Bacillus licheniformis NBRC 12195 and Lactobacillus paracasei subsp. paracasei NBRC 15889 on stainless steel coupons in different dilutions of skim milk (0.1%, 1.0% and 5.0%) was conducted. During long incubation at 30 °C, pH decreased due to bacterial development in unadjusted samples. In pH-adjusted samples, pH was kept at around 7.0 by the addition of sterile sodium hydroxide. Biofilms formed on stainless steel coupons were daily stained by 0.1% Crystal Violet solution and assessed by the evaluation of optical density. The bacterial count of the suspensions showed that the control of pH enhanced the growth of bacteria in free-floating form. In contrast, optical densities of biofilms formed in the pH-adjusted samples were significantly lower than in the pH-unadjusted samples in all of three skim milk dilutions. Comparison of maximum OD values of adhered cells at different nutrient levels also implicated that for both tested strains, thicker biofilms were formed in milk dilutions at higher nutrient levels. These results suggested that, control of milk pH and milk residue level could significantly reduce biofilm formation of the tested bacteria. © 2011 Elsevier Ltd.


Dat N.M.,Food Industries Research Institute | Manh L.D.,Food Industries Research Institute | Hamanaka D.,Kyushu University | Hung D.V.,Kyushu University | And 2 more authors.
Food Control | Year: 2014

In the dairy industry, dairy by-products such as skim milk, buttermilk and butter serum which possess different specific compositions, could contact with processing surfaces to form conditioning layers and subsequently alter bacterial attachment behavior of the surfaces. In order to simulate and elucidate this process, stainless steel coupons were conditioned with skim milk, buttermilk and butter serum solutions. Formed conditioning layers were examined under a confocal laser scanning microscope (CLSM) and the influence of surface conditioning on bacterial adherence was investigated. The results showed that different conditioning layers were formed by different dairy by-products. The layer formed by skim milk, buttermilk and butter serum was the thinnest, medium and the thickest, respectively. The treatment of stainless steel surfaces with skim milk, buttermilk and butter serum could reduce the adherence of dairy-related bacteria (Lactococcus lactis subsp. lactis NBRC 100933, Leuconostoc mesenteroides subsp. cremoris NBRC 107766 and Lactobacillus casei FIRI 108) at different levels. In the majority of cases, the adherence-reducing ability of buttermilk and butter serum was found better than skim milk. While skim milk could reduce bacterial adherence during shorter exposure time (almost of 30min), buttermilk and butter serum could act during the longer period (up to 720min). The result suggested that, bacterial adherence-reducing effect of buttermilk and butter serum may correlate to their substances associated with milk fat globule membrane. In order to decrease bacterial adherence, surface conditioning with skim milk, buttermilk and butter serum is recommended. Surface conditioning with skim milk is suitable for short bacterial exposure time (30min), for a longer period of time (more than 180min), only surface conditioning with buttermilk and with butter serum is advisable. © 2014 Elsevier Ltd.


PubMed | Food Industries Research Institute
Type: Journal Article | Journal: International journal of systematic and evolutionary microbiology | Year: 2013

Yeasts of the genus Moniliella were isolated from 651 flower samples collected in Vietnam, using an enrichment medium containing 50% glucose. Species of the genus Moniliella were found in 5% of the samples and 54 strains were isolated. The strains were identified based on D1/D2 LSU rRNA gene sequences as M. megachiliensis (15 strains), M. dehoogii (14 strains), and M. mellis (2 strains). The remaining 23 strains could not be reliably placed under any known species. Among them, 12 strains isolated from flowers of Ipomoea pes-caprae and Calotropis gigantea were peculiar for the intensive formation of chlamydospores. These strains could be subdivided into pigmented and non-pigmented groups. Both groups were identical in PCR fingerprints generated with primer (GAC)5 and in D1/D2 and ITS sequences. The yeast was closely related to M. fonsecae but differed from the latter by 52 nt (or 10.3% of divergence) in the D1/D2 sequence and 71 nt (or 16.9% of divergence) in the ITS sequence. The name Moniliella byzovii sp. nov. is proposed for this novel species. The type strain is TBY 2041.7(T)=CBS 12757(T)=NRRL Y-63661(T). The MycoBank number is MB 803186.

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