PDF(Pubmed)
Abstract：
This study investigated the first-ever reported use of freshwater Nannochloropsis for the bioremediation of dairy processing side streams and co-generation of valuable products, such as β-galactosidase enzyme. In this study, N. limnetica was found to grow rapidly on both autoclaved and non-autoclaved whey-powder media (referred to dairy processing by-product or DPBP) without the need of salinity adjustment or nutrient additions, achieving a biomass concentration of 1.05-1.36 g L-1 after 8 days. The species secreted extracellular β-galactosidase (up to 40.84 ± 0.23 U L-1) in order to hydrolyse lactose in DPBP media into monosaccharides prior to absorption into biomass, demonstrating a mixotrophic pathway for lactose assimilation. The species was highly effective as a bioremediation agent, being able to remove > 80% of total nitrogen and phosphate in the DPBP medium within two days across all cultures. Population analysis using flow cytometry and multi-channel/multi-staining methods revealed that the culture grown on non-autoclaved medium contained a high initial bacterial load, comprising both contaminating bacteria in the medium and phycosphere bacteria associated with the microalgae. In both autoclaved and non-autoclaved DPBP media, Nannochloropsis cells were able to establish a stable microalgae-bacteria interaction, suppressing bacterial takeover and emerging as dominant population (53-80% of total cells) in the cultures. The extent of microalgal dominance, however, was less prominent in the non-autoclaved media. High initial bacterial loads in these cultures had mixed effects on microalgal performance, promoting β-galactosidase synthesis on the one hand while competing for nutrients and retarding microalgal growth on the other. These results alluded to the need of effective pre-treatment step to manage bacterial population in microalgal cultures on DPBP. Overall, N. limnetica cultures displayed competitive β-galactosidase productivity and propensity for efficient nutrient removal on DPBP medium, demonstrating their promising nature for use in the valorisation of dairy side streams.
摘要：
这项研究调查了有史以来首次报道的使用淡水微球藻进行乳品加工侧流的生物修复和有价值的产品的热电联产，如β-半乳糖苷酶。在这项研究中,发现N.limnetica在高压灭菌和非高压灭菌的乳清粉培养基（称为乳制品加工副产品或DPBP）上都能迅速生长，而无需调整盐度或添加营养素。8天后达到1.05-1.36gL-1的生物量浓度。该物种分泌细胞外β-半乳糖苷酶（高达40.84±0.23UL-1），以便在吸收到生物质之前将DPBP培养基中的乳糖水解为单糖，证明了乳糖同化的混合营养途径。该物种作为生物修复剂非常有效，在所有培养物中,能够在两天内去除DPBP培养基中>80%的总氮和磷酸盐。使用流式细胞术和多通道/多染色方法进行的种群分析显示，在非高压灭菌培养基上生长的培养物含有较高的初始细菌负荷，包括培养基中的污染细菌和与微藻相关的藻圈细菌。在高压灭菌和非高压灭菌的DPBP介质中，微藻细胞能够建立稳定的微藻-细菌相互作用,抑制细菌接管并在培养物中成为优势种群（占总细胞的53-80％）。微藻优势的程度，然而,在非高压灭菌介质中不那么突出。这些培养物中的高初始细菌载量对微藻性能有混合影响，一方面促进β-半乳糖苷酶的合成，另一方面竞争营养并阻碍微藻的生长。这些结果暗示需要有效的预处理步骤来管理DPBP上的微藻培养物中的细菌群体。总的来说,N.limnetica培养物显示出竞争性的β-半乳糖苷酶生产率和在DPBP培养基上有效去除养分的倾向，证明了它们在乳制品侧流的增值中的有前途的性质。
