Bioremediation potential of formaldehyde by the marine microalga Nannochloropsis oculata ST-3 strain

Biotechnology progress for removal of indoor gaseous formaldehyde

Formaldehyde is a ubiquitous carcinogenic indoor pollutant. The treatment of formaldehyde has attracted increasing social attention. Over the past few decades, an increasing number of publications have reported approaches for removing indoor formaldehyde. These potential strategies include physical adsorption, chemical catalysis, and biodegradation. Although physical adsorption is widely used, it does not really remove pollution. Chemical catalysis is very efficient but adds the risk of introducing secondary pollutants. Biological removal strategies have attracted more research attention than the first two methods, because it is more efficient, clean, and economical. Plants and bacteria are the common organisms used in formaldehyde removal. However, both have limitations and shortcomings when used alone. This review discusses the mechanisms, applications, and improvements of existing biological methods for the removal of indoor gaseous formaldehyde. A combination strategy relying on plants, bacteria, and physical adsorbents exhibits best ability to remove formaldehyde efficiently, economically, and safely. When this combination system is integrated with a heating, ventilation, air conditioning, and cooling (HVAC) system, a practical combined system can be established in formaldehyde removal. Multivariate interactions of biological and non-biological factors are needed for the future development of indoor formaldehyde removal. KEY POINTS: • Indoor gaseous formaldehyde removal is necessary especially for new residence. • Biological removal strategies have attracted increasing research attentions. • Combined system of plants, bacteria, and physical adsorbents exhibits best efficiency. • Integrated device of biological and non-biological factors will be potential practical.

The toxicity of continuous long-term low-dose formaldehyde inhalation in mice

Although the toxicity of high-dose formaldehyde (FA) inhalation has been extensively analyzed in animals, the effect of continuous long-term exposure to low-dose FA has not been well documented. This study aims to evaluate the toxicity of continuous long-term low-dose FA inhalation in mice. Forty-eight Kunming male mice were equally randomized to three groups according to the dose of FA inhalation exposure: a control (0 mg/m³) group, a low-dose (0.08 mg/m³) group and a high-dose (0.8 mg/m³) group. The mice have been selected to expose to FA for different consecutive days at 24 h/day. The learning and memory functions, pathological changes in the lung and liver, and the percentage of CD4 ⁺ T and CD8 ⁺ T cells were observed and analyzed. It was found that continuous long-term inhalation of FA at relatively low doses could impair the learning and memory functions and induce pathological changes in the lung and liver, but did not seem to significantly affect the number of immune (CD4 ⁺ T and CD8 ⁺ T) cells.

Biodegradation of high concentrations of formaldehyde by lyophilized cells of Methylobacterium sp. FD1

In the present study, Methylobacterium sp. FD1 utilizing formaldehyde was isolated from soil. The resting cells of FD1 degraded high concentrations of formaldehyde (~2.7 M) and produced formic acid and methanol that were molar equivalents of one-half of the degraded formaldehyde. This result suggests that formaldehyde degradation by FD1 is caused by formaldehyde dismutase. The optimal temperature and pH for formaldehyde degradation by the resting cells of FD1 were 40 °C and 5–7, respectively. The lyophilized cells of FD1 also degraded high concentrations of formaldehyde. The formaldehyde degradation activity of the lyophilized cells was maintained as the initial activity at 25 °C for 287 days. These results suggest that the lyophilized cells of FD1 are useful as formaldehyde degradation materials.

Formaldehyde biodegradation by immobilized Methylobacterium sp. XJLW cells in a three-phase fluidized bed reactor

In the present study, the ability of a newly isolated strain, Methylobacterium sp. XJLW to degrade formaldehyde was investigated in shake flasks and in a bioreactor. The resting cells of Methylobacterium sp. XJLW showed high formaldehyde tolerance (60 g L(-1)) and high degradation rate (1,687.5 mg L(-1) h(-1)) in shake flasks. This biodegradation was initiated by a dismutation reaction since formic acid was formed and caused significant dropping of pH in the media. The addition of CaCO(3) to the media was found as an effective strategy to control the pH and keep the cells in high degradation bioactivity. A three-phase fluidized bed reactor (TPFBR) was designed to test the formaldehyde-biodegrading ability of immobilized Methylobacterium sp. XJLW. Using a repeated-batch degradation mode, the immobilized cells were able to degrade 5 g L(-1) formaldehyde (with a maximal degradation rate of 464.5 mg L(-1) h(-1) under the optimum conditions) and showed stable bioactivity after 20 batches of reuse in the TPFBR.