Towards the Anaerobic Production of Surfactin Using Bacillus subtilis

The anaerobic growth of B. subtilis to synthesize surfactin poses an alternative strategy to conventional aerobic cultivations. In general, the strong foam formation observed during aerobic processes represents a major obstacle. Anaerobic processes have, amongst others, the distinct advantage that the total bioreactor volume can be exploited as foaming does not occur. Recent studies also reported on promising product per biomass yields. However, anaerobic growth in comparison to aerobic processes has several disadvantages. For example, the overall titers are comparably low and cultivations are time-consuming due to low growth rates. B. subtilis JABs24, a derivate of strain 168 with the ability to synthesize surfactin, was used as model strain in this study. Ammonium and nitrite were hypothesized to negatively influence anaerobic growth. Ammonium with initial concentrations up to 0.2 mol/L was shown to have no significant impact on growth, but increasing concentrations resulted in decreased surfactin titers and reduced nitrate reductase expression. Anaerobic cultivations spiked with increasing nitrite concentrations resulted in prolonged lag-phases. Indeed, growth rates were in a similar range after the lag-phase indicating that nitrite has a neglectable effect on the observed decreasing growth rates. In bioreactor cultivations, the specific growth rate decreased with increasing glucose concentrations during the time course of both batch and fed-batch processes to less than 0.05 1/h. In addition, surfactin titers, overall YP/X and YP/S were 53%, ∼42%, and ∼57% lower than in serum flask with 0.190 g/L, 0.344 g/g and 0.015 g/g. The YX/S, on the contrary, was 30% lower in the serum flask with 0.044 g/g. The productivities q were similar with ∼0.005 g/(g⋅h). However, acetate strongly accumulated during cultivation and was posed as further metabolite that might negatively influence anaerobic growth. Acetate added to anaerobic cultivations in a range from 0 g/L up to 10 g/L resulted in a reduced maximum and overall growth rate μ by 44% and 30%, respectively. To conclude, acetate was identified as a promising target for future process enhancement and strain engineering. Though, the current study demonstrates that the anaerobic cultivation to synthesize surfactin represents a reasonable perspective and feasible alternative to conventional processes.

TECHNOLOGY OF INACTIVATION OF MICROORGANISMS IN FOOD PRODUCTS

Предложена технология производства консервированных продуктов питания на водной основе. Технология инактивирования микроорганизмов и прекращения аэробных процессов в продуктах питания основана на использовании модернизированного технологического оборудования и химических веществ. Устройство для обработки электрическим током (омический нагрев) позволяет ингибировать размножение микроорганизмов – мезофильных, термофильных бактерий и плесневых грибов при кратковременном хранении сырья. Устройство для магнитной обработки воды обеспечивает: повышение проницаемости биологических мембран клеток; изменение водородных связей; увеличение электропроводности воды; ускорение процесса и усиление в 1,6–2 раза растворимости моющего средства в воде при помывке упаковочной тары. Устройство для замедления микробиологических процессов увеличивает срок хранения продуктов питания в жидких средах при температуре окружающего воздуха 20–22°С до 8 сут без использования холодильного оборудования. Модернизация устройства для замедления микробиологических процессов способствует сокращению в 2 раза электроэнергии, расходуемой на прекращение развития микроорганизмов. Для достижения поставленной цели в состав ингредиентов включено химическое вещество. Использование в технологии лекарственного препарата (аспирин) повышает эффективность прекращения аэробных процессов. Воздействие постоянного электрического тока позволяет прекратить микробиологические процессы при заданных параметрах: частота f 50 Гц, напряжение U 36 В, сила тока I0,9–1 A. Установлено снижение активности развития микроорганизмов. Исключена возможность распространения микробиологической порчи от одной партии к другой. Повышена проницаемость мембран тканевых клеток. Увеличен срок хранения продуктов питания без ухудшения качественных показателей до 3 лет. Предложено устройство, позволяющее осуществить хранение продуктов питания на водной основе без использования холодильного оборудования. A technology for the production of canned food products on a water basis has been proposed. The technology of inactivation microorganisms and the cessation of aerobic processes in food products is based on the use of modernized technological equipment and chemicals. The device for processing by an electric current (ohmic heating) allows to stop the reproduction of microorganisms (mesophilic, thermophilic bacteria and mold fungi) during short term storage of raw materials. The device for magnetic treatment of water provides an increase in the permeability of biological membranes of cells; change of hydrogen bonds; increases the electrical conductivity of water; accelerates the process and increases 1,6–2 times the solubility of the detergent in water when washing the packaging. The device for slowing down microbiological processes increases the shelf life of food products in liquid media, at an ambient temperature of 20–22°C for up to 8 days without the use of refrigeration equipment. Modernization of the device to slow down microbiological processes contributes to a 2-fold reduction in the amount of electricity consumed to stop the development of microorganisms. To achieve this goal, a chemical was included in the ingredients. Use in the technology of the drug (aspirin) increases the effectiveness of stopping aerobic processes. The effect of a constant electric current makes it possible to stop microbiological processes at specified parameters (frequency f 50 Hz, voltage U 36 V, current I 0,9–1 A). The activity of microorganism development was reduced is established. The possibility of spreading microbiological damage from one batch to another is excluded. The permeability of membranes of cells of fabrics is increased. The period of storage of products without deterioration of quality indicators is increased to 3 years. A device that allows storing food products on a water basis without the use of refrigeration equipment is proposed.

Tolerance of roach for modified water mineralization levels and temperatures expressed by biochemical indicators

Changes in the activity of Na+/K+-ATPase, lactate dehydrogenase, and succinate dehydrogenase in the white muscles and gill petals of roach, Rutilus rutilus (L), were studied for the combined actions of water mineralization and water temperature. It was established that decreased mineralization to 260.0 mg dm-3 and increased water temperature to 32°C increased aerobic processes in roach tissues. A sharp increase in water temperature and changes in water mineralization significantly affected the tolerance and physiological state of fish and could impact their abundance in waterbodies.

Cryptic oxygen cycling in anoxic marine zones

Oxygen availability drives changes in microbial diversity and biogeochemical cycling between the aerobic surface layer and the anaerobic core in nitrite-rich anoxic marine zones (AMZs), which constitute huge oxygen-depleted regions in the tropical oceans. The current paradigm is that primary production and nitrification within the oxic surface layer fuel anaerobic processes in the anoxic core of AMZs, where 30–50% of global marine nitrogen loss takes place. Here we demonstrate that oxygenic photosynthesis in the secondary chlorophyll maximum (SCM) releases significant amounts of O2to the otherwise anoxic environment. The SCM, commonly found within AMZs, was dominated by the picocyanobacteriaProchlorococcusspp. Free O2levels in this layer were, however, undetectable by conventional techniques, reflecting a tight coupling between O2production and consumption by aerobic processes under apparent anoxic conditions. Transcriptomic analysis of the microbial community in the seemingly anoxic SCM revealed the enhanced expression of genes for aerobic processes, such as nitrite oxidation. The rates of gross O2production and carbon fixation in the SCM were found to be similar to those reported for nitrite oxidation, as well as for anaerobic dissimilatory nitrate reduction and sulfate reduction, suggesting a significant effect of local oxygenic photosynthesis on Pacific AMZ biogeochemical cycling.