Twenty-two lactic acid bacteria （LAB） strains isolated from Argentinean goat dairy products were evaluated for its biochemical properties and esterase activities relevant to flavor development. Streptococcus thermop...Twenty-two lactic acid bacteria （LAB） strains isolated from Argentinean goat dairy products were evaluated for its biochemical properties and esterase activities relevant to flavor development. Streptococcus thermophilus （UNSE314）, Lactobacillus （L.） delbrueckii subsp, bulgaricus （UNSE309）, L. rhamnosus （UNSE308）, L. plantarum （UNSE287, UNSE316, UNSE317） and Pediococcus pentosaceus （UNSE315） strains presented high acidifying activity. All strains tested metabolized citrate and produced diacetyl-acetoin in goat milk. Based on these results, 10 strains with the best performance in diverse technological properties were selected to determine esterolytic activity. In all evaluated strains, esterase specific activity （ESA） was detected on ct-naphthyl （ct-NA） acetate and 13-naphthyl （[3-NA） acetate, propionate, eaprylate and ct-NA butyrate. No activity was detected on [3-NA laurate. The highest values were detected when using a-NA instead of fI-NA derivatives as substrate. In Pediocoecus strains, wide variability in ESA were observed, which were species- and strain-specific. These results allow us to select strains with biochemical properties and esterase activities to design starter and adjunct cultures that contribute to flavor development during cheese ripening, thus preserving the typical organoleptic characteristics of Argentinean goat cheeses.展开更多
Rice straw is supposed to be an environment-friendly biomaterial for inhibiting the growth of harmful blooms of the cyanobacterium Microcystis aeruginosa. However, its potential mechanism is not well known. To explore...Rice straw is supposed to be an environment-friendly biomaterial for inhibiting the growth of harmful blooms of the cyanobacterium Microcystis aeruginosa. However, its potential mechanism is not well known. To explore this mechanism, the growth, cell viability(esterase activity, membrane potential, and membrane integrity), photosynthesis, and cell size of M. aeruginosa were determined using fl ow cytometry and Phyto-PAM after exposure to rice straw extracts(RSE). The results show that doses from 2.0 to 10.0 g/L of RSE effi ciently inhibited the alga for 15 days, while the physiologic and morphologic responses of the cyanobacteria were time-dependent. RSE interfered with the cell membrane potential, cell size, and in vivo chlorophyll- a fl uorescence on the fi rst day. After 7 days of exposure, RSE was transported into the cytosol, which disrupted enzyme activity and photosynthesis. The cyanobacteria then started to repair its physiology(enzyme activity, photosynthesis) and remained viable, suggesting that rice straw act as an algistatic agent.展开更多
Magnolia denudata(M. denudata) leaf litter extract(MDLLE) was tested on the response of Microcystis aeruginosa(M. aeruginosa). The inhibition of M. aeruginosa increased from 7.6% to 49.8% at 0.4 g·L^(-1) dosage w...Magnolia denudata(M. denudata) leaf litter extract(MDLLE) was tested on the response of Microcystis aeruginosa(M. aeruginosa). The inhibition of M. aeruginosa increased from 7.6% to 49.8% at 0.4 g·L^(-1) dosage while it increased from 15.7% to 77.4 % at 2.0 g·L^(-1) dosage during 15 days of incubation. The parameter variation of relative electron transport rate(rETR), maximal quantum yield(Fv/Fm ), and electron transport rates(rERTmax) indicated that photosynthesis was an important target impaired by MDLLE, including the photosynthetic center photosystem II(PSII) of M. aeruginosa which demonstrated from the rapid light curves(RLCs). The results of Chlorophyll-a(Chl-a) fluorescence, RLCs, and fluorescein diacetate(FDA) staining assays were consistent with those of growth inhibition tests. The results demonstrated that the application of MDLLE offered great potential on cyanobacterial blooms control especially at the initial stage of development. Furthermore, several kinds of volatile chemicals had been isolated in MDLLE, and the role on suppression of growth for M. aeruginosa should be further studied separately.展开更多
文摘Twenty-two lactic acid bacteria （LAB） strains isolated from Argentinean goat dairy products were evaluated for its biochemical properties and esterase activities relevant to flavor development. Streptococcus thermophilus （UNSE314）, Lactobacillus （L.） delbrueckii subsp, bulgaricus （UNSE309）, L. rhamnosus （UNSE308）, L. plantarum （UNSE287, UNSE316, UNSE317） and Pediococcus pentosaceus （UNSE315） strains presented high acidifying activity. All strains tested metabolized citrate and produced diacetyl-acetoin in goat milk. Based on these results, 10 strains with the best performance in diverse technological properties were selected to determine esterolytic activity. In all evaluated strains, esterase specific activity （ESA） was detected on ct-naphthyl （ct-NA） acetate and 13-naphthyl （[3-NA） acetate, propionate, eaprylate and ct-NA butyrate. No activity was detected on [3-NA laurate. The highest values were detected when using a-NA instead of fI-NA derivatives as substrate. In Pediocoecus strains, wide variability in ESA were observed, which were species- and strain-specific. These results allow us to select strains with biochemical properties and esterase activities to design starter and adjunct cultures that contribute to flavor development during cheese ripening, thus preserving the typical organoleptic characteristics of Argentinean goat cheeses.
基金Supported by the National Basic Research Program of China(973 Program)(No.2008CB418002)the National Major Science and Technology Program for Water Pollution Control and Treatment(No.2012ZX07103-002)+1 种基金the CAS/SAFEA International Partnership Program for Creative Research Teams of Chinese Academy of Sciences(No.KZZDEW-TZ-08-01)the National Natural Science Foundation of China(No.20807043)
文摘Rice straw is supposed to be an environment-friendly biomaterial for inhibiting the growth of harmful blooms of the cyanobacterium Microcystis aeruginosa. However, its potential mechanism is not well known. To explore this mechanism, the growth, cell viability(esterase activity, membrane potential, and membrane integrity), photosynthesis, and cell size of M. aeruginosa were determined using fl ow cytometry and Phyto-PAM after exposure to rice straw extracts(RSE). The results show that doses from 2.0 to 10.0 g/L of RSE effi ciently inhibited the alga for 15 days, while the physiologic and morphologic responses of the cyanobacteria were time-dependent. RSE interfered with the cell membrane potential, cell size, and in vivo chlorophyll- a fl uorescence on the fi rst day. After 7 days of exposure, RSE was transported into the cytosol, which disrupted enzyme activity and photosynthesis. The cyanobacteria then started to repair its physiology(enzyme activity, photosynthesis) and remained viable, suggesting that rice straw act as an algistatic agent.
基金National Natural Science Foundation of China(No.51378316)Science and Technology Project of Shenzhen Polytechnic,China(No.6020320001K0)Urban Smart Water Pollution Prevention and Control Technology Development Center by the Department of Education of Guangdong Province,China(No.2019GGCZX007)。
文摘Magnolia denudata(M. denudata) leaf litter extract(MDLLE) was tested on the response of Microcystis aeruginosa(M. aeruginosa). The inhibition of M. aeruginosa increased from 7.6% to 49.8% at 0.4 g·L^(-1) dosage while it increased from 15.7% to 77.4 % at 2.0 g·L^(-1) dosage during 15 days of incubation. The parameter variation of relative electron transport rate(rETR), maximal quantum yield(Fv/Fm ), and electron transport rates(rERTmax) indicated that photosynthesis was an important target impaired by MDLLE, including the photosynthetic center photosystem II(PSII) of M. aeruginosa which demonstrated from the rapid light curves(RLCs). The results of Chlorophyll-a(Chl-a) fluorescence, RLCs, and fluorescein diacetate(FDA) staining assays were consistent with those of growth inhibition tests. The results demonstrated that the application of MDLLE offered great potential on cyanobacterial blooms control especially at the initial stage of development. Furthermore, several kinds of volatile chemicals had been isolated in MDLLE, and the role on suppression of growth for M. aeruginosa should be further studied separately.
