Study On Efficiency For Photosynthetic Bacterial Z08 Treating Soybean Protein Wastewater

Photosynthetic bacteria(PSB) wastewater treatment technology has an irreplaceable advantage with removing pollutants as well as recycling bacteria resources. However, the accumulating PSB biomass in wastewater treatment process is not high and this hinders the development and reuse of recycling bacteria in PSB wastewater treatment. Therefore, a strain of PSB Rubrivivax gelatinosus Z08 isolated and purificated in previous work was used. The function factor(cultivation condition, nutrient substance, micro-element) on Z08 growth and organic pollutants removal were investigated in treating soybean wastewater treatment. Further, the possible mechanismson these influencing factors enhancing Z08 growth and organic pollutants removal were discussed by regulating the energy metabolism and material synthetic pathways in this work.In a certain range of light intensity(0-8000lux), the highest biomass production(2300mg/L) was achieved under the optimal light intensity(6000lux), at this condition, COD and protein removals were about more than 80%. The effects of different light intensity on Z08 growth were summarized in three stages: light limit(0-5000lux), light sufficiency(5000-7000lux) and light inhibition(>8000 lux). Mechanism analysis showed that the contents of bacteriochlorophyll, carotenoid, cytochrome b6, cytochrome f and ATP were enhanced in the energy metabolism of photosynthesis pathway. Moreover, increasing 1,5-diphosphate ribulose carboxylase and acetyl-Co A carboxylase activities in C3 and lipid synthesis pathways could promote Z08 growth and organic pollutants removal. Further analysis indicated that light could increase ATP production by changing four pigments contents through the regulation on inducing and starting photosynthetic genes expression in photosynthesis pathway.Research on the effects of oxygen on Z08 production showed that the optimal oxygen condition was micro-aerobic condition(0.3-0.9mg/L) among three oxygen conditions including anaerobic, micro-aerobic and aerobic. The highest biomass production was 2300mg/L, COD and protein removals were about 81%. Mechanism analysis indicated that dissolved oxygen(DO) increased succinate dehydrogenase, NADH dehydrogenase, cytochrome oxidase activity and ATP production in the energy metabolism of aerobic respiration pathway, which promoted Z08 growth and organic pollutants removal. Further analysis indicated that DO could regulate photosynthetic genes expression. Under anaerobic or micro-aerobic conditions, photosynthetic genes expression photosynthetic gene expression was not affected. However, under aerobic condition, excess DO inhibited photosynthetic genes expression, and decreased the contents of bacteriochlorophyll, carotenoid, cytochrome b6 and cytochrome f further.Research on the effects of the nutrient substance on Z08 production showed that the highest biomass production was 3000mg/L under the optimal dose(600mg/L) in a certain range of succinic acid addition(0-800mg/L). COD and protein removals reached about 85%. Mechanism analysis indicated that succinic acid increased succinate dehydrogenase activity and ATP production in the energy metabolism of photosynthesis pathway, which promoted Z08 growth and organic pollutants removal; the optimal dose was 1mg/L with the highest biomass production(3600mg/L) when the triacontanol concentration ranged from 0 to 1.5mg/L. COD and protein removals reached about 93% at the optimal dose. Mechanism analysis indicated that triacontanol increased bacteriochlorophyll, carotenoid and ATP production in the energy metabolism of aerobic respiration pathway, which promoted Z08 growth and organic pollutants removal; the optimal dose was 0.5mg/L with the highest biomass production(3600mg/L) when the triacontanol concentration ranged from 0 to 1.5mg/L. COD and protein removals reached about 93% at the optimal dose. Mechanism analysis indicated that triacontanol increased bacteriochlorophyll, carotenoid and ATP production in the energy metabolism of aerobic respiration pathway, which promoted Z08 growth and organic pollutants removal.Research on the effects of the microelement on Z08 production showed that the optimal dose was 10mg/Lwith the highest biomass production(3000mg/L) when the magnesium ion concentration ranged from 0 to 20mg/L. COD and protein removals reached about 90% at the optimal dose. Mechanism analysis indicated tha t magnesium ion increased bacteriochlorophyll, carotenoid and ATP production in the energy metabolism of photosynthesis pathway and it also enhanced fructose 1,6-double phosphatase and acetyl-Co A carboxylase activities in C3 and lipid synthesis pathways. So Z08 growth and organic pollutants removal were promoted; the optimal dose was 5mg/L with the highest biomass production(3500mg/L) when the cobalt ion concentration ranged from 0 to 7mg/L. COD and protein removals reached about 90% at the optimal dose. Mechanism analysis indicated that magnesium ion improved Z08 growth and organic pollutants removal by increasing vitamin B12 and ATP production in the energy metabolism; the optimal dose was 20mg/L with the highest biomass production(3400mg/L) when the iro n ion concentration ranged from 0 to 40mg/L. COD and protein removals reached about 91% at the optimal dose. Mechanism analysis indicated that iron ion improved increasing bacteriochlorophyll, cytochrome b6 and cytochrome f of photosynthesis pathway. It also increased ATP production by stimulating succinate dehydrogenase, NADH dehydrogenase and cytochrome oxidase activities in the energy metabolism of aerobic respiration pathway. So Z08 growth and organic pollutants removal were significantly enhanced. Further, in this study, a hypothesis was proposed that iron ion was used as one inducer to start iron sulfur cluster operon by synthesizing assembly protein and using iron and sulfur materials. Therefore one center containing cytochrome b6, cytochrome f, succinic acid dehydrogenase and NADH dehydrogenase was constituted, and it would increase ATP production. The results show that by optimizing the factors(culture conditions, plant hormones, trace elements) to improve the wastewater treatment in photosynthetic b acteria Z08 biomass production and organic matter removal, to maximize the realization in sewage resource.