Browsing by Author "Velasquez, A."

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    Bioremoval of copper by filamentous fungi isolated from contaminated soils of Puchuncavi-Ventanas Central Chile
    (2023) Carvajal, M.; Jeldres, P.; Vergara, A.; Lobaina, E.; Olivares, M.; Meza, D.; Velasquez, A.; Dorta, F.; Jorquera, F.; Seeger, M.; Cereceda-Balic, F.; Fadic, X.
    Pollution represents a high risk to plants, animals, and human beings, causing an imbalance and affecting the environment. Soil is considered a universal sink, containing the highest load of environmental pollution. Puchuncavi-Ventanas sector, decreed as a saturated contamination zone in 1993, is considered one of the most affected areas by industrial pollution and belongs to one of the 5 sacrifice zones of Chile. The localities of Puchuncavi and Ventanas have heavy metal pollution levels that exceed up to 99% of the limits allowed by Canadian standards. The objective of this study was to characterize heavy metal tolerance and removal potential of filamentous fungi isolated from polluted soils for their use in decontamination systems and in situ soil improvement. Six fungal strains were selected based on their tolerance and a high capability to accumulate heavy metals, achieving copper bioaccumulation of 84% (Mortierella sp. strain LG01), 49% (Clonostachys sp. strain CQ23) and 48-77.5% (Trichoderma sp. strain LM01A). Trichoderma sp. strain LM01A was able to remove 41% of copper from contaminated soil under ex situ conditions. Some fungal strains belong to beneficial fungal genera, which are used as bioproducts in agriculture. The results of this study highlighted the use of Trichoderma sp. in soils contaminated, which may be of special interest in agriculture due to the large amounts of copper sulfate still applied as a pesticide in Chile and the world.
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    Effects of rumen fluid pre-incubation on in vitro proteolytic activity of enzymatic extracts from rumen microorganisms
    (ELSEVIER SCIENCE BV, 2010) Velasquez, A.; Pichard, G.
    Enzymatic extracts were prepared from rumen fluid (RF) either directly after collection or after incubation in enriched media and their proteolytic activities were measured and compared The objective of RF in vitro cultivation was to augment enzymatic activity by using diverse incubation media containing different feed substrates to selectively induce microorganisms with essentially unrestricted sources of energy and N The effects on protein degradation in bovine serum albumin (BSA) and soybean meal rapeseed meal dehydrated alfalfa meal and perennial ryegrass were determined Enzymatic extracts were characterized by means of protease zymograms Two adult Holstein Friesian rumen fistulated cows were used as RF donors Standard anaerobic incubation techniques in buffer-mineral media were used and protein degradation was measured as residual true protein after enzymatic incubations Results reveal an effect of RF pre-incubation on protein degradation (P<0 0001) measured in BSA and in feed substrates and also on the hydrolysis rate (P<0 001) measured with native substrates only The enzymatic extracts showed a high potential for proteolytic degradation reaching 785 mg/g crude protein (CP) degraded in BSA after 12h of incubation and 830 mg/g CP degraded in soybean meal with 48h of incubation compared to only 654 mg/g and 414 mg/g in controls The zymograms of these extracts revealed six zones of proteolytic activity with the highest concentration of peptidases in the zone of high molecular weight (117 and 130 kDa) In vitro pre-incubation of rumen fluid in culture media enriched with energy and N sources allowed collection of enzymatic extracts with higher proteolytic activity than extracts obtained directly from fresh rumen fluid (C) 2010 Elsevier B V All rights reserved