Evaluation of various Bacillus coagulans isolates for the production of high purity L‐lactic acid using defatted rice bran hydrolysates

• Published in: International journal of food science & technology Vol. 54; no. 4; pp. 1321 - 1329
• Main Authors: Alexandri, Maria, Neu, Anna‐Katrin, Schneider, Roland, López‐Gómez, José Pablo, Venus, Joachim
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01-04-2019
• Subjects: Acid production; Acids; Bacillus coagulans; defatted rice bran; enantiomeric purity; enzymatic hydrolysis; fermentation; Glucose; Hydrolysates; Lactic acid; Nutrient content; Proteins; Purity; Rice bran; Starch; Substrates
• ISSN: 0950-5423; 1365-2621
• DOI: 10.1111/ijfs.14086

Summary
Defatted rice bran (DRB) constitutes an abundant by‐product stream, generated during rice milling and subsequent bran oil extraction. Enzymatic hydrolysis of starch and protein content in DRB was optimised in terms of solid loading. Among the four solid loadings evaluated (10%, 15%, 20% and 25%), the hydrolysate derived from 20% solids resulted in the highest concentration of glucose (82.3 g L−1) and free amino nitrogen (234.8 mg L−1). The fermentability of the hydrolysate was evaluated via screening of sixteen isolates. All the strains were able to grow and produce high purity L‐lactic acid, utilising the DRB as sole carbon and nutrient source. Among the studied strains, the Bacillus coagulans A107 isolate presented the most promising results in terms of final lactic acid concentration (75.9 g L−1), yield (0.90 g g−1) and productivity (2.7 g L−1 h−1). The results of this study indicate that DRB could be employed as an inexpensive, alternative substrate for L‐lactic acid production.
Defatted rice bran is rich in starch and protein, which were hydrolysed to glucose and free amino nitrogen. The hydrolysate was tested as complete fermentation medium for lactic acid production using thermophilic B. coagulans isolates. Isolate A107 produced highly optical pure L‐lactic acid.