全面供光策略调控废水培养光合细菌产单细胞蛋白

Comprehensive light strategy for regulating photosynthetic bacteria in wastewater treatment systems for single-cell protein production

为拓展蛋白质来源,缓解中国饲料蛋白资源短缺现状,该研究通过供光策略调控强化了沼泽红假单胞菌(R.palustris)从废水中回收菌体资源及单细胞蛋白(single cell protein, SCP)的效果,并解析了不同供光策略下物质合成与污染物降解之间的相关性。结果表明:在白炽灯、120μmol/(m^(2)·s)的光强及18 h光/6 h暗(L/D)的光周期条件下菌体的生物量及日产量可达(1 140.56±19.72) mg/L及(0.32±0.02) g/(L·d),相较于24 L/0 D、 3 L/21 D及9 L/15 D组分别提高了17.06%~93.21%、54.43%~299.93%(P<0.05);在白炽灯、120 μmol/(m^(2)·s)的光强及3 h光/21 h暗的光周期条件下,菌体的蛋白质质量分数最高,为67.47%,相较于其他所有试验组提高了21.96%~44.54%(P<0.05)。化学需氧量(chemical oxygen demand, COD)和氨氮(ammonia nitrogen, NH_(4)^(+)-N)去除率在白炽灯、120 μmol/(m^(2)·s)的光强及18 h光/6 h暗的光周期条件下可达72.03%~78.40%。相关性分析表明,光强、光质分别与蛋白质含量及浓度呈显著负相关;而光周期与蛋白质浓度呈显著正相关,因此,光周期是R. palustris从废水体系中提升SCP产量的有效调控方法。该研究为提高废水体系中光合细菌合成SCP提供了新的方法与思路。

New protein resources can be developed to alleviate the shortage of protein in the feed industry.Photosynthetic bacteria(PSB)can serve as unique microbial protein sources.Among them,the light environment is a crucial influencing factor in the growth and metabolism of PSB.In this study,the light supply strategies were employed to enhance the growth of Rhodopseudomonas palustris(R.palustris)and the synthesis of single-cell protein(SCP)in the wastewater resource systems of PSB.Additionally,a systematic analysis was made on the correlations between substance synthesis and pollutant degradation under different light supply strategies.The results indicated that a full spectrum of light was more conducive to the accumulation of biomass and protein concentration in R.palustris,compared with the segmented spectra.Under incandescent lamp and white LED irradiation,the highest biomass concentration,daily bacterial production,bacterial yield,and protein concentration reached(1023.18±201.17)mg/L,(0.32±0.10)g/(L·d),(0.31±0.03)mg/mg and(555.66±9.18)mg/L,respectively.These values increased by 37.26%-43.79%,108.82%-137.92%,42.01%-91.85%,and 24.77%-33.47%,respectively,compared with the blue and green light groups(P<0.05).Moderate light intensity was favored to accumulate biomass and protein concentration,while excessive or low intensity was detrimental to the accumulation of high-value products by R.palustris.Specifically,under a light intensity of 120μmol/(m^(2)·s),the highest biomass concentration,daily bacterial production,bacterial yield,and protein concentration reached(1646.12±2.47)mg/L,(0.77±0.01)g/(L·d),(0.44±0.05)mg/mg and(803.59±2.62)mg/L,respectively.There was an increase of 60.23%-140.19%in biomass and an increase of 61.90%-94.18%in protein concentration,compared with the 0μmol/(m^(2)·s)(control)and 240μmol/(m^(2)·s)groups(P<0.05).Intermittent light exhibited significant advantages over continuous light.An appropriate light cycle was selected to significantly promote the growth and protein synthesis of R.palustris.In the condition of 18 L/6 D,the highest biomass concentration,daily bacterial production,protein concentration,and nitrogen conversion efficiency reached(1140.56±19.72)mg/L,(0.32±0.02)g/(L·d),(506.53±48.20)mg/L,and(1.77±0.35)mg/mg,respectively.There were increases by 17.06%-93.21%,54.43%-299.93%,24.35%-43.88%and 38.78%,respectively,compared with the 3 L/21 D and 9 L/15 D groups(P<0.05).The 3 L/21 D group exhibited the highest protein content at 67.47%,indicating an increase of 21.96%-44.54%,compared with all the other experimental groups(P<0.05).Additionally,under conditions of incandescent light,the light intensity of 120μmol/(m^(2)·s)and photoperiod of 18 L/6 D,COD and NH_(4)^(+)-N removal efficiencies reached 72.03%-78.40%.Furthermore,there were significant negative correlations between light intensity and spectrum with the protein content and concentration.Conversely,the photoperiod shared a significant positive correlation with protein concentration.Therefore,the photoperiod can be expected to enhance the production of SCP by R.palustris.Its mechanism involves the direct regulation of PSB growth and metabolism by the light/dark cycle.During the light period,PSB pigments capture photons through photoreactions,driving electron transfer,generating electrical energy,and ultimately converting it into ATP;Simultaneously,the Calvin cycle efficiency is enhanced,leading to the accumulation of cell growth and SCP.During the dark period,PSB cells focus on the division process,increasing overall biomass.This research can provide innovative insights to enhance the SCP synthesis in wastewater systems using PSB.