High Loading Degradation of Poly(lactide)/Thermoplastic Starch Blend Film Using Mixed-Enzymes Produced by Fed-Batch Culture of Laceyella sacchari LP175

Abstract

Purpose: Co-production of poly(l-lactide) (PLLA)-degrading enzyme and raw starch-degrading enzyme (RSDE) was investigated using a fed-batch culture of Laceyella sacchari LP175 in a 10.0 L airlift fermenter. Agricultural products were used as substrates for production of enzymes to degrade the poly(lactide)/thermoplastic starch blend film at high concentration. Methods: Fed-batch culture was performed in a 10.0 L airlift fermenter for co-production of PLLA-degrading enzyme and RSDE by L. sacchari LP175. Parameters affecting PLA/thermoplastic starch (TPS) blend film at high loading (100 g/L) degradation were optimized using response surface methodology (RSM) with a central composite design (CCD) at 50 °C for 24 h. Results: Maximum enzyme production of PLLA-degrading enzyme and RSDE at 91.6 ± 7.21 and 120.1 ± 9.33 U/mL, respectively, were obtained when incubated at 50 °C for 42 h after adding raw cassava starch (3.34 g/L) and PLA powder (0.52 g/L) at 30 h of cultivation. The optimum conditions for degradation (92.23%) from the model were enzyme concentration at 0.6% (w/v), time to add CaCO3 3 h after digestion and 0.2 M of Tris-HCl buffer (pH 9.0) in the shaking flask scale with a 95% significance level (p < 0.05). These conditions gave the highest degradation at 90.65 ± 4.03% from the actual experimental. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) revealed the mixed enzymes produced by L. sacchari LP175 hydrolyzed PLA/TPS blend film at 50 °C. Conclusions: Results indicated the feasibility of producing mixed enzymes by L. sacchari LP175 and hydrolysis of PLA/TPS blend film at high concentration to reduce waste accumulation through biotechnological processes. Graphical Abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer Nature B.V.