Preparation of PHA (polyhydroxyalkanoates) from a citric residue
The present invention relates to an obtainment process of biodegradable polymers from a citric residue resulting from the processing of orange juice. The polymers obtained are polyesters classified as polyhydroxyalkanoates including, among them the poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate). The biodegradable polymer is obtained from the batch culture process or fed batch culture process with or without recirculation of the cells, using as a carbon source the pre-treated pressing liquor and/or the citric molasses. The polyhydroxyalkanoates, herein described, can be used as substitutes of the synthetic polyesters in different areas, including the food, pharmaceutical, medical, agricultural and other areas.
1. Obtainment process of polyhydroxcyalkanoate (PHA) from the citric residue, wherein it comprises the following steps:
a) obtaining a pressing liquor and/or citric molasses;
b) physical-chemical treating of the material obtained in the step a to obtain a supernatant material;
c) preparing a culture medium for the production of PHA wherein in the step c, the culture medium is prepared through an addition of essential nutrients to the culture process to the supernatant material and the added nutrients are selected among nitrogen, phosphor, sulphur, magnesium, potassium, oxygen, oligonutrients or a mixture of them;
d) conducting a culture process on said culture medium at a temperature of 25° C. to 40° C., and wherein the oligonutrients are selected among molybdenum, manganese, cobalt, zinc, nickel, copper and boron, and a mixture of them.
2. Obtainment process of PHA in accordance to claim 1 , wherein the citric residue corresponds to the skin, pulp and seed resulting from the oranges pressing to the juice extraction.
3. Obtainment process of PHA in accordance to claim 1 , wherein in the step a, the pressing liquor is obtained from the milling/treatment with calcium oxide or agents that have the property to hydrolyze the pectin and pressing of the citric residue.
4. Obtainment process of PHA in accordance to claim 1 , wherein in the step a, the citric molasses is obtained from the concentration of the pressing liquor followed by cooling.
5. Obtainment process of PHA in accordance to claim 4 , wherein the concentration of the pressing liquor is performed through evaporation.
6. Obtainment process of PHA in accordance to claim 1 , wherein in the step b the physical-chemical treatment of the pressing liquor and/or citric molasses occurs through the following sub-steps:
b1) centrifugation of the pressing liquor and/or citric molasses;
b2) sterilization or pasteurization of the material;
b3) decantation of the sterilized or pasteurized material, followed by the removal of the supernatant material.
7. Obtainment process of PHA in accordance to claim 6 , wherein a correction step of pH of the pressing liquor and/or citric molasses is performed before the step b1.
8. Obtainment process of PHA in accordance to claim 1 , wherein a sterilization or pasteurization step of the material takes place after the addition of nutrients to the culture medium.
9. Obtainment process of PHA in accordance to claim 1 , wherein in the step c, the culture medium comprises an initial content of reductor sugars of 10 to 60 g·L −1 .
10. Obtainment process of PHA in accordance to claim 1 , wherein in the step d, the culture process is conducted through a batch culture process or fed batch culture process.
11. Obtainment process of PHA in accordance to claim 10 , wherein the batch culture process or fed batch culture process is performed with a recirculation of the cells.
12. The Obtainment process of PHA from a citric acid residue comprising the steps of:
a) obtaining a pressing liquor and/or citric molasses;
b) physical-chemical treating of the material obtained in the step a;
c) preparing a culture medium for the production of PHA;
d) conducting a culture process on said culture medium;
wherein in the step d, the culture process takes place in the following steps:
d1) step of cellular growth;
d2) step of production induction of PHA, and wherein in the step d2, the induction to the production of PHA is initiated through the non-carbon sources nutrients limitation.
13. Obtainment process of PHA in accordance to claim 1 , wherein in the step d, the pH can vary between 7.2 and 5.4.
14. Obtainment process of PHA in accordance to claim 1 , wherein in the step d, the medium is agitated at a velocity from 200 to 1000 rpm.
15. Obtainment process of PHA in accordance to claim 1 , wherein in the step d, the diluted oxygen concentration must be between 10% and 100% of the culture medium saturation with atmospheric air.
16. Obtainment process of PHA in accordance to claim 12 , wherein at the beginning of the induction step, the concentration of the minimum biomass corresponds from 15 g·L −1 to 60 g·L −1 .
17. Obtainment process of PHA in accordance to claim 12 , wherein the non-carbon sources nutrients are selected among nitrogen, phosphor, sulphur, magnesium, potassium or oxygen.
18. Usage of citric residue for the production of PHA, wherein it occurs through the process as defined in claim 1 .