Fermentative hydrogen production by conventionally and unconventionally heat pretreated seed cultures: A comparative assessment

In this study, the effects of pretreatment temperature and time during conventional and unconventional, microwave-assisted heat shock on the hydrogen producing capability of anaerobic seed sludge from soluble starch was focused. It was found that the different heat transfer techniques resulted in seed cultures with comparable hydrogen production potentials, with the highest obtainable values of approximately 0.9 L H2/L-d. A comprehensive, statistical analysis revealed that both treatment temperature and time could be designated as significant process variables, however, in distinguishable extents for the two alternative methods. The results indicated that microwave-based sludge pretreatment needed remarkably shorter curing times (2 min) to eliminate H2-consuming, methanogenic activity in comparison to the conventional heat shock method (30 min). It was also demonstrated that microwave irradiation increased the soluble organic matter content in the seed sludge. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

Kinetic study on hydrolysis of various pectins by Aspergillus niger polygalacturonase

Hydrolysis of pectins from various sources by a polygalacturonase (PG) enzyme was studied from a kinetic point of view. Pectin substrates – which are commercially not available – were extracted from sugar beet pulp, apple, red currant and black currant. Strong product inhibition was found in each pectin preparations that could be described by a competitive mechanism. The kinetic parameters (Michaelis-Menten constants, maximal reaction rates and inhibition constants) were determined and compared. Differences in the parameters imply distinctions in structure of the pectins studied

The Effect of Different Pretreatment Methods and Operational Conditions on the Biohydrogen Production Potential of Aged Anaerobic Culture

In this study, the preconditioning of anaerobic culture by aging was carried out followed by testing various pretreatments (heat shock and alkali) to improve H2 production. It has turned out that aging could enhance the hydrogen generation meanwhile heat- and alkali curing led to comparable H2 formation activity with a slight advantage of the former one. Subsequently, the heat treated microflora was applied under different pHs and Gas to Liquid phase ratios and according to the statistical analysis both were significant factors since they affected not only the hydrogen productivity but also the developing H2 partial pressures in the system. Furthermore, an indirect relationship between hydrogen productivity and hydrogen partial pressure was found, which means that higher H2 turnouts were associated with lower H2 partial pressure conditions. The PCR-DGGE analysis of the microbial community after heat- and alkali pretreatments showed the dominancy of Clostridium species