Domestication of plants and animals is the foundation for feeding the world population. We report that domestication of the model yeast S. cerevisiae reprogrammed its life cycle entirely. We tracked growth, gamete formation and cell survival across many environments for nearly 1000 genome sequenced isolates and found a remarkable dichotomy between domesticated and wild yeasts. Wild yeasts near uniformly trigger meiosis and sporulate when encountering nutrient depletions, whereas domestication relaxed selection on sexual reproduction and favoured survival as quiescent cells. Domestication also systematically enhanced fermentative over respiratory traits while decreasing stress tolerance. We show that this yeast domestication syndrome was driven by aneuploidies and gene function losses that emerged independently in multiple domesticated lineages during the specie's recent evolutionary history. We found domestication to be the most dramatic event in budding yeast evolution, raising questions on how much domestication has distorted our understanding of this key model species.
Multienzyme complex has attracted increased attention in biofuel technology. They offer solutions to effective degradation of complex plant material into fermentable sugars. Microorganisms, especially bacteria and fungi, are well studied for their ability to produce enzymes complex unlike yeast. Yeast strain isolated from mushroom farm was studied for simultaneous production of cellulase, xylanase and ligninase enzymes using lignocellulose waste as substrates. A response surface methodology (RSM) involving Box-Behnken design (BBD) was used to investigate interaction between variables (moisture content, inoculum size, initial pH, incubation time) that affect enzyme production. Crude filtrate was partially purified and characterised. Yeast strain identified as
Saccharomyces cerevisiae
SCPW 17 was finally studied. Evaluation of lignocellulose waste for enzyme complex production revealed corn cob to be most effective substrate for cellulase, xylanase and ligninase production with enzyme activity of 17.63 ± 1.45 U/gds, 29.35 ± 1.67 U/gds and 150.75 ± 2.01 μmol/min respectively. Time course study showed maximum enzyme complex production was obtained by day 6 with cellulase activity of 12.5 U/gds, xylanase 48.3 U/gds and ligninase 90.8 μmol/min. Using RSM involving BBD, maximum enzyme activity was found to be 19.51 ± 0.32 U/gds, 56.86 ± 0.38 U/gds, 408.17 ± 1.04 μmol/min for cellulaase, xylanase and ligninase respectively. The developed models were highly significant at probability level of P = 0.0001 and multiple correlation co-efficient (R
2
) was 0.9563 for cellulase, 0.9532 for xylanase and 0.9780 for ligninase. Enzyme complex was stable at varying pH and temperature conditions.
Saccharomyces cerevisiae
(SCPW 17) studied produced enzyme complex which can be used for bioconversion of biomass to value-added chemicals.
Nineteen fungal strains were isolated from a chicken slaughterhouse effluent and within those, only one showed high values of lipolytic activity in submerged cultures. This fungus was identified as Trametes hirsuta. The crude extract was immobilized in chitosan/clay beads, with an immobilization yield of 80.9%. The analyses of the crude extract and the immobilized derivative at different temperatures, pH (s), solvents, metallic ions and storage showed that the immobilization process increased the enzyme life span. Ethyl esters were obtained in solvent free systems using chicken viscera oil and the enzyme crude extract. For effective comparison, a reaction using viscera oil and commercial lipase Novozym 435 was carried out. The result revealed 35% and 28% esters conversion in the reactions containing chicken viscera oil, using Novozym 435 and the crude extract respectively. The extract was also used in a reaction with soybean oil, traditionally used as starting substrate for biodiesel production.
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