Isolation and identification of Penicillium chrysogenum strain Y5 and its copper extraction characterization from waste printed circuit boards.

Biohydrometallurgy is generally considered as a green technology for the recycling of industrial solid waste. In this study, an indigenous fungal strain named Y5 with the ability of high-yielding organic acids was isolated and applied in bioleaching of waste printed circuit boards (PCBs). The strain Y5 was identified as Penicillium chrysogenum by morphological and molecular identification. Meanwhile, we investigated that an optimal set of culturing conditions for the fungal growth and acids secretion was 15 g/L glucose with initial pH 5.0, temperature 25°C and shaking speed 120 rpm in shaken flasks culture. Moreover, three bioleaching processes such as one-step, two-step and spent medium processes were conducted to extract copper from waste PCBs. Spent medium bioleaching showed higher copper extraction percentage and it was 47% under 5%(w/v) pulp density. Transmission electron microscope (TEM) observation combining with energy dispersive analysis of X-rays (EDAX) showed that the leached metal ions did not obviously damage the hypha cells. All above results indicated that P.chrysogenum strain Y5 has the tolerance to metal ions, suggesting its potential in recycling of metals from waste PCBs in industry.

Recycling of metals from pretreated waste printed circuit boards effectively in stirred tank reactor by a moderately thermophilic culture.

To seek a feasible technique for processing waste printed circuit boards (PCBs), pretreatment of PCBs by table separation and further bioleached by moderate thermophiles in a stirred tank reactor were investigated. The shaking table separation, conducted after grinding and sieving of PCBs, produced two fractions: metal-rich parts (RPCBs), which is more suitable for pyrometallurgy process than untreated PCBs, and metal-poor parts (PPCBs) with only 8.83% metals was then bioleached by a mixed culture of moderate thermophiles effectively. After adaptation, the mixed culture could tolerate 80 g/L PPCBs. The bioleaching results showed that metals recovery was 85.23% Zn, 76.59% Cu and 70.16% Al in only 7 days. Trace Pb and Sn were detected in the leachate because of precipitating. The microorganism community structure was analyzed by amplified ribosomal DNA restriction analysis. Two moderately thermophilic bacteria species were identified as Leptospirillum ferriphilum and Acidithiobacillus caldus. Furthermore, uncultured Thermoplasmatales archaeon was also detected in the leaching system. It was also shown that moderate thermophiles revealed best bioleaching ability when compared with mesophiles and the mixture of mesophiles and moderate thermophiles. Finally, we designed a two-stage process model according to the present study to achieve semi-industrial waste PCBs recycling and economic feasibility analysis indicated that the process was profitable.

Metallosphaera tengchongensis sp. nov., an acidothermophilic archaeon isolated from a hot spring.

Two novel acidothermophilic archaea, strains Ric-A(T) and Ric-F, were isolated from muddy water samples of a sulfuric hot spring located in Tengchong County, Yunnan Province, PR China. The strains were aerobic and facultatively chemolithoautotrophic. Both strains could oxidize S(0) and K2S4O6 for autotrophic growth, and could use organic materials for heterotrophic growth. Growth was observed at 55-75 °C and pH 1.5-6.5. The strains could oxidize metal sulfide ores, showing their potential in bioleaching. The DNA G+C contents of strains Ric-A(T) and Ric-F were 41.8 and 41.6 mol%, respectively. Analysis of 16S rRNA gene sequences showed that the two strains shared 99.8 % sequence similarity to each other, but <97 % to other known species of the genus Metallosphaera. DNA-DNA hybridization indicated that the isolates were different strains of a novel species of the genus Metallosphaera. Strains Ric-A(T) and Ric-F also shared a number of physiological and biochemical characteristics that distinguished them from recognized species of the genus Metallosphaera. On the basis of phenotypic, chemotaxonomic and phylogenetic comparisons with their closest relatives, it was concluded that strains Ric-A(T) and Ric-F represent a novel species of the genus Metallosphaera, for which the name Metallosphaera tengchongensis sp. nov. is proposed. The type strain is Ric-A(T) ( = NBRC 109472(T) = CGMCC 1.12287(T)).