NOVELTY - Integrated process for producing bio-oil involves: growing at least one phototrophic microalga in ponds/containers (A) containing water and nutrients; growing at least one heterotrophic microalga in ponds/containers (B) in presence of carbohydrates and/or proteins transported by suspension from biomass hydrothermal treatment; recovering both the biomass with growth water, and subjecting to thickening and thermal treatment; recovering oil fraction (12) that can be transformed into biofuel; and supplying resulting aqueous suspension (4) to heterotrophic microalga.    USE - As integrated process for producing bio-oil from both phototrophic and heterotrophic microorganisms, which is useful for forming bio-fuel (claimed).    ADVANTAGE - The method provides biomass derived from microalgae, cultivated so as to maximize their lipid content, which when suitably extracted, can be used as raw material for bio-oil to be fed to industrial plants for production of biofuels. The bio-oil produced from microalgae, hence offers advantage of not being in competition with crops for nutritional use. Also, production of bio-oil from microalgae is advantageous with respect to cultivation from agricultural crops as it allows greater production of oil per hectare of surface per year; where the method utilizes both phototrophic microalga which use solar light and CO2 as energy source, and heterotrophic microalga which use carbon source such as carbohydrates and/or proteins, in the absence of light, rather than the prior art technology using phototrophic micro-organisms alone. A disadvantage of phototrophic microalgae is that they grow with low density. As aqueous suspension becomes more opaque and less transparent to light, with increase in concentration of algal mass, growth diminishes until it stops above certain concentration. The necessity of favoring penetration of light also limits maximum depth of ponds to few tens of cm. The low concentration of algal mass, per liter of aqueous suspension, and low depth of ponds involve use of large volumes of water and relatively extensive surfaces and hence high costs and energy consumptions for separation and extraction of bio-oil, or alternatively, relatively low productive yields to bio-oil. Also, heterotrophic microalgae, also in consortium with other micro-organisms, do not use light for production of algal biomass and consequently their concentration in aqueous medium does not suffer from light penetration limit in growth medium. As they grow in dark, they require energy and carbon source alternative to light and CO2. This source based on carbohydrates and possibly proteins, is not always easily available at competitive costs. The integrated process for producing bio-oil from both phototrophic and heterotrophic microorganisms, is able to combine advantages of both phototrophic and heterotrophic microorganism production, and overcomes relative disadvantages. In the method phototrophic microalgae are utilized to produce algal biomass, using light and carbon dioxide, from which bio-oil can be separated together with aqueous suspension consisting of polysaccharides and protein aggregates. For extraction of bio-oil, biomass is conveniently subjected to hydrothermal treatment which promotes separation of oil phase and transformation of polysaccharides and protein aggregates into carbohydrates and simple proteins, which can be more easily used for feeding and growing biomass from heterotrophic microalgae, which are also producers of bio-oil. As heterotrophic microalgae can reach very high concentrations in growth water, it is possible to produce bio-oil from microalgae using much lower overall quantity of water than that which would be used with cultivation of phototrophic microalgae alone. A second advantage of method is that it requires lower cultivation surface with respect to use of phototrophic microalgae alone with same production of bio-oil.    DETAILED DESCRIPTION - Integrated process for producing bio-oil from both phototrophic and heterotrophic microorganisms, involves:    (A) growing at least one phototrophic microalga, in ponds/containers (A) containing water and nutrients and a device adapted to distribute carbon dioxide in the water mass;    (B) growing at least one heterotrophic microalga, in consortium with other microorganisms, in ponds/containers (B) containing water and nutrients in presence of carbohydrates and/or proteins transported by a suspension coming from a hydrothermal treatment of biomass;    (C) recovering both the phototrophic and heterotrophic developed biomass with its growth water, and subjecting the global suspension thus obtained to thickening, at least up to 5 wt.%, in a thickening section (C);    (D) subjecting the thickened suspension (9) to thermal treatment at 80-350 degrees C and pressure of 0.1-25 MPa, for greater than or equal to 1 minute;    (E) recovering, after cooling the thermally treated thickened suspension, an oil fraction (12) adapted to be transformed into bio-fuel; and    (F) supplying the resulting aqueous suspension (4), rich in carbohydrates and proteins, assimilable by the heterotrophic microalgae, to the step (B).    DESCRIPTION OF DRAWING(S) - The figure shows a scheme of enclosed figure and quantification sheet for the integrated process for producing bio-oil from both phototrophic and heterotrophic microorganisms.    Cultivation ponds/containers of phototrophic microalgae (A)    Cultivation ponds/containers of heterotrophic microalgae (B)    Thickening section of suspension comprising algal mass (C)    Pressurized container (D)    Separator for recovery of bio-oil (E)    Heat exchange sections (F1, F2, F3)    Heat generator (G)    Aqueous suspension (4)    Thickened suspension (9)    Bio-oil (12)