2 results
Search Results
Now showing 1 - 2 of 2
- ItemProcess disturbances in agricultural biogas production—causes, mechanisms and effects on the biogas microbiome: A review(Basel : MDPI AG, 2019) Theuerl, S.; Klang, J.; Prochnow, A.Disturbances of the anaerobic digestion process reduce the economic and environmental performance of biogas systems. A better understanding of the highly complex process is of crucial importance in order to avoid disturbances. This review defines process disturbances as significant changes in the functionality within the microbial community leading to unacceptable and severe decreases in biogas production and requiring an active counteraction to be overcome. The main types of process disturbances in agricultural biogas production are classified as unfavorable process temperatures, fluctuations in the availability of macro- and micronutrients (feedstock variability), overload of the microbial degradation potential, process-related accumulation of inhibiting metabolites such as hydrogen (H 2 ), ammonium/ammonia (NH 4 + /NH 3 ) or hydrogen sulphide (H 2 S) and inhibition by other organic and inorganic toxicants. Causes, mechanisms and effects on the biogas microbiome are discussed. The need for a knowledge-based microbiome management to ensure a stable and efficient production of biogas with low susceptibility to disturbances is derived and an outlook on potential future process monitoring and control by means of microbial indicators is provided.
- ItemProduction and purification of L-lactic acid in lab and pilot scales using sweet sorghum juice(Basel : MDPI AG, 2019) Olszewska-Widdrat, A.; Alexandri, M.; López-Gómez, J.P.; Schneider, R.; Mandl, M.; Venus, J.Sweet sorghum juice (SSJ) was evaluated as fermentation substrate for the production of l-lactic acid. A thermophilic Bacillus coagulans isolate was selected for batch fermentations without the use of additional nutrients. The first batch of SSJ (Batch A) resulted on higher lactic acid concentration, yield and productivity with values of 78.75 g·L−1, 0.78 g·g−1 and 1.77 g·L−1 h−1, respectively. Similar results were obtained when the process was transferred into the pilot scale (50 L), with corresponding values of 73 g·L−1, 0.70 g·g−1 and 1.47 g·L−1 h−1. A complete downstream process scheme was developed in order to separate lactic acid from the fermentation components. Coarse and ultra-filtration were employed as preliminary separation steps. Mono- and bipolar electrodialysis, followed by chromatography and vacuum evaporation were subsequently carried out leading to a solution containing 905.8 g·L−1 lactic acid, with an optical purity of 98.9%. The results of this study highlight the importance of the downstream process with respect to using SSJ for lactic acid production. The proposed downstream process constitutes a more environmentally benign approach to conventional precipitation methods.