Higher Bioavailability of Organic Bound Zinc from High Zinc-Enriched Fungi

Abstract

The organic forms of trace elements are considered more bioavailable than the inorganic forms. Although yeast can enrich metal elements and convert inorganic zinc to organic species, its tolerability and transforming capacity are limited. It would therefore be very interesting to look for higher conversion and accumulation in zinc fungi to obtain organic bound zinc from the natural environment. In this paper, potato dextrose agar (PDA) medium containing 800 μg/mL zinc was used for initial screening, with twenty-two fungal strains that tolerated high zinc isolated from the natural environment, and one strain (No.LZ-1108) growing well at a zinc (II) concentration of 10,000 μg/mL. According to morphological analysis, 18S rDNA sequence analysis, and biophysical and biochemical characteristics, No.LZ-1108 was tentatively identified as Fusarium oxysporum. Using atomic absorption spectrometry, the zinc content in the No.LZ-1108 cells was found to be 6.7 mg/g dry cell. After oral administration to rats at a dose of 10 mg Zn (II)/kg body weight, the area under the plasma concentration-time curve (AUC) and the maximum zinc blood concentration (Cmax) of No.LZ-1108 and zinc gluconate were 8.10 g/L.min and 4.28 g/L.min, 23.72 μg/mL and 6.23 μg/mL, respectively. The AUC of No.LZ-1108 was significantly higher than those of zinc gluconate (P<0.05), and the mean relative bioavailability of AUC(test)/AUC(zinc gluconate) was 190 %, which showed that the bound zinc in No.LZ-1108 was more bioavailable than zinc gluconate. The present study reports an interesting alternative to developing zinc-based supplements from a natural source of zinc.

Candida tropicalis sp. Nov., a novel, zinc-enriched yeast species found in China

“…In our previous studies, we have shown that Fusarium oxysporum has greater accumulation of zinc, with a higher bioavailability than the supplement zinc gluconate (Zhang et al, 2014). Following on from this, we have conducted extensive screening and discovered a new strain belonging to the genus Candida, which also possess the zinc enriching activity and in this paper, we describe this novel yeast species and examine its ability to enrich zinc.…”

“…The following thermal cycling program was used; 32 cycles of 3 min at 94 °C, 30 s at 94 °C, 30 s at 56 °C, 50 s at 72 °C, followed by 7 min at 72 °C. The amplified PCR products were separated by 1% agarose gel electrophoresis and sent to Shanghai Biotech Bioengineering Technology Services for sequencing (Zhang et al, 2014). After obtaining the sequence, a BLAST search was performed and 10 strain sequences with similar homology were found (Altschul et al, 1990).…”

“…Each blood sample was treated with a 14 M nitric and 10 M perchloric acid mixture (4:1, v/v) by boiling it until a clear solution was obtained. The zinc content was measured using an atomic absorption spectrophotometer (AAS-3200, Shanghai, China) (Zhang et al, 2014). The measurement conditions were: lamp current 5 mA, wavelength 248.3 nm, nip 0.2 nm, air flow 13.5 L/min, acetylene flow 2.00 L/min.…”

“…Zinc(Zn) is one of the most essential and indispensable trace elements in cells (Chasapis et al, 2012). It plays an important role in numerous enzyme systems and is involved in multiple biological pathways such as enzymatic catalysis, redox regulation, cellular signal transduction, the immune system and neurons (Zhang et al, 2014). In the immune system, zinc is essential for innate immunity (which is mediated by cell), phagocytosis, and the function of the immune-specific cells; neutrophils, natural killer cells, and macrophages.…”

“…is used to prevent and treat zinc deficiency. Microbial transformation is one of the most important methods used to assist zinc supplementation and Saccharomyces cerevisiae has been often used as a delivery vehicle for trace elements supplements because of its ability to accumulate metals and convert inorganic metals into organic species (Wang et al, 2011;Zhang et al, 2014). Some studies have shown that the zinc in zinc-enriched yeast has higher bioavailability than other supplements such as zinc sulfate and zinc gluconate (Tompkins et al, 2007), and also has lower toxicity (Wang et al, 2011).…”