Society growing awareness of excessive sugar consumption impact in health has led to an increased attention towards several sugar substitutes. Despite the existing alternatives in the market, D-tagatose possesses unique features. The enzymatic isomerization of D-galactose has achieved more projection as it is a more environmentally friendly compared to chemical isomerization. On the other hand, the search of renewable sources of D-galactose is necessary to attain a sustainable growth. Nevertheless, D-galactose production from renewable resources requires a pre-treatment that includes a hydrolysis of polysaccharides or disaccharides to obtain monomer sugars. Thus, the main objective of this thesis was the production of D-tagatose from several renewable resources by enzymatic isomerization of D-galactose using a L-arabinose isomerase from Bacillus subtilis (BSAI). For that, production and purification of BSAI enzyme was performed. Moreover, Gelidium amansii, κ-carrageenan and cheese whey were evaluated as sources of D-galactose by acid and enzymatic hydrolysis of complex sugars. BSAI was produced and purified with a yield of 34 mg/g cell. Moreover, isomerase activity for D-galactose substrate was verified by HPLC (High performance liquid chromatography). The BSAI enzyme was used for D-tagatose production from D-galactose obtained from several raw materials. Regards, red seaweed pre-treatment for D-galactose production, 12% (w/w) of biomass using a ratio of 0.125 g of sulphuric acid/g at 150 ºC for 10 min was suitable for the extraction of galactan as galactose achieving a concentration of 22.28 g/L. On other hand, optimization of hydrolysis of κ-carrageenan was performed by an experimental design. Under selected conditions (sulphuric acid concentration of 2.25% (w/w) and a treatment time of 45 minutes), percentage of hydrocolloid was increased to 8% (w/w) in order to obtain a liquor with approximately 20 g/L of D-galactose. Finally, cheese whey powder was enzymatically hydrolysed using a lactase (5UI/g of lactose) achieving 26.67 g/L of D-galactose. For liquors from Gelidium amansii there are no significant differences in the conversion between the use of detoxified and non-detoxified liquors. So, HMF did not inhibited the action of the BSAI enzyme. For the same BSAI concentration (7 mg/mL) conversions of 50.9, 52.0, 55.6 and 27.8% were obtained in the isomerization assays with Gelidium amansii detoxified and non-detoxified liquor, cheese whey hydrolysate and κ-carrageenan hydrolysate, respectively. The results obtained are very similar to those obtained in the group previously with pure galactose solutions. Thus, the use of liquors instead of pure solutions does not affect BSAI enzyme activity.