## 1 Introduction
First, the compost's heat and moisture attack the PLA chains, splitting them apart until lactic acid is produced. After that, the microorganisms in the soil mineralize the polymer fragments and lactic acid into methane under anaerobic conditions and carbon dioxide under aerobic conditions [24; 25; 26]. Table 1 shows examples of microorganisms capable of metabolizing glycerol to lactic acid. To decrease the cost of the raw materials needed for fermentation, several strategies are being investigated. Different wastes have also been used to produce lactic acid, for instance, for the production of L-(+)-lactic acid with high enantiomeric purity, achieved by using _B. coagulans_ A166, [PERSON] et al. [22] have analyzed the possibility of fermentation with hydrolyses derived from the organic fraction of a municipal solid waste, resulting in 61.1 g\(\cdot\)L\({}^{-1}\) of lactic acid and a yield of 0.94 g\(\cdot\)g\({}^{-1}\). [PERSON] et al. [23] used an agricultural lignocellulosic biomass (rice straw) as a fermentation substrate to produce D-(\(-\))-lactic acid by employing _Lactobacillus delbrueckii_, producing 46.6 g\(\cdot\)L\({}^{-1}\) of lactic acid, and a yield of 0.92 g\(\cdot\)g\({}^{-1}\) with 99.5% of optical purity. [PERSON] et al. [33] also evaluated the production of D-(\(-\))-lactic acid by _Sporolactobacillus inulinus_ YBS1-5, using cotonseed meal and corncob residue, reaching 107.2 g\(\cdot\)L\({}^{-1}\) of lactic acid with a yield of 0.85 g\(\cdot\)g\({}^{-1}\). Lactic acid is also an interesting alternative to acrylic acid and alkyl acrylate production from renewable sources. It is possible to produce acrylates by dehydrating lactic acid, using heterogeneous catalysis with zeolites and hydroxyapatite, minimizing the dependence on petrochemical sources to produce important acrylate-based monomers [34; 35; 36]. In this context, this research aimed to isolate new strains of bacteria capable of biocconverting glycerol into lactic acid and 1,3-propanediol, molecules of high biotechnological interest. The present work was able to isolate and identify a wild bacteria strain from the Brazilian biome (_K. pneumoniae_), which was capable of metabolizing glycerol to L-(+)-lactic acid with 100% optical purity and 1,3-propanediol, without requiring genetic modification of the microorganism. The study directed the main metabolic pathway of the microorganism to produce the product of interest (lactic acid) by changing fermentation parameters such as pH, temperature and inoculum concentration. In addition, a factorial design strategy was used to verify the optimal conditions for glycerol consumption and L-(+)-lactic acid production. Although 1,3-propanediol is a value-added chemical with numerous applications in the food, cosmetics and textile sectors, in the present work, we chose to control and optimize the generation of lactic acid. The production of just one of \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Microorganism** & **Substrate** & **Lactic Acid** & **Yield** & **Productivity** & **Reference** \\  & **Concentration (g\(\cdot\)L\({}^{-1}\))** & **(g\(\cdot\)g\({}^{-1}\))** & **(g\(\cdot\)L\({}^{-1}\).h\({}^{-1}\))** & **Reference** \\ \hline _Komagataella phiffi Strains_ & glycerol & 70.0 & 0.665 & 1.39 & [27] \\ _Escherichia coli AC-521_ & glycerol & 90.4 & 0.88 & 1.13 & [28] \\ _Enterococcus faecalis_ & waste glycerol from & 15.8 & 0.37 & 0.61 & [29] \\ _Lactobacillus reuteri DSM_ & glycerol and glucose & 50.44 & 0.78 & 1.50 * & [30] \\ _Enterococcus faecalis strain W11_ & glycerol & 135.0 & 0.9 & 0.87 & [31] \\ _Lactobacillus reuteri_ & glycerol and glucose & 6.0 & 0.536 & 0.28 & [32] \\ \hline \hline \end{tabular}  
* mM\(\cdot\)mL\({}^{-1}\)-h\({}^{-1}\).  
\end{table} 
Table 1: Examples of fermentation with glycerol as a carbon source to obtain lactic acid. the organic acids would facilitate the purification process and avoid competition for the carbon source.