Abstract：
This study performed microbial analysis of nutrient film technique (NFT) hydroponic systems on three indoor farms in Singapore (the \"what\"). To justify the necessity of sanitizing hydroponic systems, strong biofilm-forming bacteria were isolated from the facility and investigated for their influence on Salmonella colonization on polyvinyl chloride (PVC) coupons in hydroponic nutrient solutions (the \"why\"). Finally, sanitization solutions were evaluated with both laboratory-scale and field-scale tests (the \"how\"). As a result, the microbiome composition in NFT systems was found to be highly farm specific. The strong biofilm formers Corynebacterium tuberculostearicum C2 and Pseudoxanthomonas mexicana C3 were found to facilitate the attachment and colonization of Salmonella on PVC coupons. When forming dual-species biofilms, the presence of C2 and C3 also significantly promoted the growth of Salmonella (P < 0.05). Compared with hydrogen peroxide (H2O2) and sodium percarbonate (SPC), sodium hypochlorite (NaOCl) exhibited superior efficacy in biofilm removal. At 50 ppm, NaOCl reduced the Salmonella Typhimurium, C2, and C3 counts to <1 log CFU/cm2 within 12 h, whereas neither 3% H2O2 nor 1% SPC achieved this effect. In operational hydroponic systems, the concentration of NaOCl needed to achieve biofilm elimination increased to 500 ppm, likely due to the presence of organic matter accumulated during crop cultivation and the greater persistence of naturally formed multispecies biofilms. Sanitization using 500 ppm NaOCl for 12 h did not impede subsequent plant growth, but chlorination byproduct chlorate was detected at high levels in the hydroponic solution and in plants in the sanitized systems without rinsing.
OBJECTIVE: This study\'s significance lies first in its elucidation of the necessity of sanitizing hydroponic farming systems. The microbiome in hydroponic systems, although mostly nonpathogenic, might serve as a hotbed for pathogen colonization and thus pose a risk for food safety. We thus explored sanitization solutions with both laboratory-scale and field-scale tests. Of the three tested sanitizers, NaOCl was the most effective and economical option, whereas one must note the vital importance of rinsing the hydroponic systems after sanitization with NaOCl.
OBJECTIVE: This study\'s significance lies first in its elucidation of the necessity of sanitizing hydroponic farming systems. The microbiome in hydroponic systems, although mostly nonpathogenic, might serve as a hotbed for pathogen colonization and thus pose a risk for food safety. We thus explored sanitization solutions with both laboratory-scale and field-scale tests. Of the three tested sanitizers, NaOCl was the most effective and economical option, whereas one must note the vital importance of rinsing the hydroponic systems after sanitization with NaOCl.
摘要：
这项研究对新加坡三个室内农场的营养膜技术（NFT）水培系统进行了微生物分析（“什么”）。为了证明水培系统消毒的必要性，从该设施中分离出强的生物膜形成细菌，并研究了它们对水培营养液中聚氯乙烯（PVC）试样上沙门氏菌定植的影响（“为什么”）。最后,通过实验室规模和现场规模的测试(“如何”)评估消毒溶液。因此,发现NFT系统中的微生物组组成具有高度的农场特异性。发现了强大的生物膜形成物，可促进沙门氏菌在PVC试片上的附着和定植。当形成双物种生物膜时，C2和C3的存在也显著促进了沙门氏菌的生长(P<0.05)。与过氧化氢（H2O2）和过碳酸钠（SPC）相比，次氯酸钠（NaOCl）在去除生物膜方面表现出优异的效果。在50ppm时，NaOCl减少了鼠伤寒沙门氏菌，C2和C3在12小时内计数至<1logCFU/cm2，而3%H2O2和1%SPC都没有达到这种效果。在可操作的水培系统中，实现生物膜消除所需的NaOCl浓度增加到500ppm，可能是由于在作物种植过程中积累的有机物的存在以及自然形成的多物种生物膜的更大持久性。使用500ppmNaOCl消毒12小时不会阻碍随后的植物生长，但是在水培溶液和未经冲洗的消毒系统中的植物中，氯化副产物氯酸盐的含量很高。
目的：本研究的意义首先在于阐明水培养殖系统消毒的必要性。水培系统中的微生物组，虽然大部分是非致病性的，可能是病原体定植的温床，因此对食品安全构成风险。因此，我们通过实验室规模和现场规模的测试探索了消毒解决方案。在三个测试过的消毒剂中，NaOCl是最有效和经济的选择，然而，必须注意用NaOCl消毒后冲洗水培系统的重要性。
目的：本研究的意义首先在于阐明水培养殖系统消毒的必要性。水培系统中的微生物组，虽然大部分是非致病性的，可能是病原体定植的温床，因此对食品安全构成风险。因此，我们通过实验室规模和现场规模的测试探索了消毒解决方案。在三个测试过的消毒剂中，NaOCl是最有效和经济的选择，然而，必须注意用NaOCl消毒后冲洗水培系统的重要性。
