A process for recovering and recycling alkyl sulfonic acid in the production of lipids from biomass deriving from Guayule plants comprising the following steps: (a) obtaining a hydrolysate comprising 5-carbon sugars from the biomass deriving from Guayule plants, by treating said biomass with an aqueous solution of at least one alkyl sulfonic acid having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms, more preferably methanesulfonic acid (CH 3 -SO 3 H); (b) contacting the hydrolysate obtained in step (a) with a weak anion exchange resin obtaining the adsorption of said at least one alkyl sulfonic acid in said weak anion exchange resin and an aqueous solution comprising 5-carbon sugars; (c) regenerating said weak anion exchange resin with an aqueous ammonium hydroxide solution obtaining an aqueous solution comprising the ammonium salt of said alkyl sulfonic acid and ammonium ions; (d) subjecting the aqueous solution comprising the ammonium salt of said alkyl sulfonic acid and ammonium ions obtained in step (c) to vacuum evaporation obtaining a solution comprising the ammonium salt of said alkyl sulfonic acid and ammonium ions, said ammonium ions being present in an amount lower than or equal to 50%, preferably between 10% and 20%, with respect to the total amount of ammonium ions present in the aqueous solution obtained in step (c); (e) contacting the solution containing the ammonium salt of said alkyl sulfonic acid and ammonium ions obtained in step (d) with a strong cation exchange resin obtaining a concentrated aqueous solution of said alkyl sulfonic acid; (f) recycling the concentrated solution of said alkyl sulfonic acid obtained at said step (e) at the aforesaid step (a). (a) obtaining a hydrolysate comprising 5-carbon sugars from the biomass deriving from Guayule plants, by treating said biomass with an aqueous solution of at least one alkyl sulfonic acid having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms, more preferably methanesulfonic acid (CH 3 -SO 3 H); (b) contacting the hydrolysate obtained in step (a) with a weak anion exchange resin obtaining the adsorption of said at least one alkyl sulfonic acid in said weak anion exchange resin and an aqueous solution comprising 5-carbon sugars; (c) regenerating said weak anion exchange resin with an aqueous ammonium hydroxide solution obtaining an aqueous solution comprising the ammonium salt of said alkyl sulfonic acid and ammonium ions; (d) subjecting the aqueous solution comprising the ammonium salt of said alkyl sulfonic acid and ammonium ions obtained in step (c) to vacuum evaporation obtaining a solution comprising the ammonium salt of said alkyl sulfonic acid and ammonium ions, said ammonium ions being present in an amount lower than or equal to 50%, preferably between 10% and 20%, with respect to the total amount of ammonium ions present in the aqueous solution obtained in step (c); (e) contacting the solution containing the ammonium salt of said alkyl sulfonic acid and ammonium ions obtained in step (d) with a strong cation exchange resin obtaining a concentrated aqueous solution of said alkyl sulfonic acid; (f) recycling the concentrated solution of said alkyl sulfonic acid obtained at said step (e) at the aforesaid step (a).