1. Bioshell calcium oxide (BiSCaO) water

Bioshell calcium oxide (BiSCaO) water

The main component of scallop shells is calcium carbonate (CaCO

₃), which is converted to CaO when heated above 800 °C. Heated scallop shell powder is composed mainly of CaO and is called "bioshell calcium oxide (BiSCaO)", a material exhibiting broad antimicrobial activity against various pathogenic bacteria

), which is converted to CaO when heated above 800 °C. Heated scallop shell powder is composed mainly of CaO and is called “bioshell calcium oxide (BiSCaO)”, a material exhibiting broad antimicrobial activity against various pathogenic bacteria

^[1][2]

, avian influenza virus

^[3]

, heat-resistant bacterial spores

^[4]

, fungi

^[5]

, and biofilms

^[6][7]

. In addition, BiSCaO is used as an additive to prolong the shelf life of food products

^[1]

. BiSCaO itself is poorly water-soluble under strongly alkaline conditions (pH > 12.3). Consequently, water suspensions containing a high concentration of BiSCaO tends to plug spray nozzles due to precipitation

^[8]

.

In this study, we explored the possibility to test whether water containing highly concentrated BiSCaO can be made using commercially available BiSCaO (over 99.6% CaO is included), since a highly concentrated BiSCaO is thought be more potent against various infectious viruses and pathogenic bacteria. We added 10 wt% BiSCaO to pure water in a bottle and then collected the supernatant. The same volume of pure water was gently poured onto the BiSCaO precipitate accumulated in the bottle and the supernatant was carefully collected. This process was repeated fifty times. The resultant BiSCaO suspension contained smaller nanoparticles (100–200 nm in diameter), and was colorless and transparent with pH > 12.7. We call this "BiSCaO Water".

In this study, we explored the possibility to test whether water containing highly concentrated BiSCaO can be made using commercially available BiSCaO (over 99.6% CaO is included), since a highly concentrated BiSCaO is thought be more potent against various infectious viruses and pathogenic bacteria. We added 10 wt% BiSCaO to pure water in a bottle and then collected the supernatant. The same volume of pure water was gently poured onto the BiSCaO precipitate accumulated in the bottle and the supernatant was carefully collected. This process was repeated fifty times. The resultant BiSCaO suspension contained smaller nanoparticles (100–200 nm in diameter), and was colorless and transparent with pH > 12.7. We call this “BiSCaO Water”.

2. In Vitro Assay for the Disinfection Activity of BiSCaO Water against Pathogenic Bacterias and Viruses

In Vitro Assay for the Disinfection Activity of BiSCaO Water against Pathogenic Bacterias and Viruses

Bactericidal activities of BiSCaO against

Escherichia coli

(

E. coli

) NBRC 3972,

E. coli

O-157:H7,

P. aeruginosa

,

Salmonella,

and

Staphylococcus aureus

(

S. aureus

) were evaluated by the Japan Food Research Laboratory (JFRL; Tokyo, Japan) (Table 1). The levels (colony forming units; CFU) of

E. coli

,

P. aeruginosa,

and

Salmonella

were reduced to below the detection limit within 5 min, 99% of

E.

coli

O-157:H7 was eliminated after 5 min, and 97% of

S. aureus

(a Gram positive bacterium) was eliminated after 5 min and reduced to below the detection limit after 15 min.

Table 1.

Assay of the activity of BiSCaO Water against pathogenic microbes in vitro.

< 10*: nondetected, ―: not determined. CFU: colony forming units

The virucidal activities of BiSCaO Water against influenza A

(H1N1), an enveloped virus, and

Feline calicivirus,

a nonenveloped virus, were evaluated using the fifty-percent tissue culture infectious dose (TCID

₅₀

) method

^[9][10]

, which was performed by JFRL (Table 2).

Feline calicivirus

treated with BiSCaO Water was reduced to below the detection limit within 1 min, and influenza A was reduced from 6.0 to 1.7 (TCID

₅₀

/mL)

at 1 min compared with the control, and then reduced to below the detection limit after 5 min

.

Table 2.

Assay of the activity of BiSCaO Water against an enveloped virus and a nonenveloped virus.

< 1.5*: nondetected, ―: not determined. TCID

₅₀

: tissue culture infectious dose

3. Conclusions

Conclusions

BiSCaO Water contains nanoparticles and is colorless and transparent, with a pH > 12.7.  BiSCaO Water completely eliminated various pathogenic bacteria within 15 min and viruses within 5 min in in vitro assays. Furthermore, BiSCaO Water exhibited higher deodorization of tainted meat and higher microbicidal efficacy using suspensions contaminated with normal bacteria compared to ethanol, BiSCaO and BiSCa(OH)

₂

suspensions, povidone iodine, NaClO, BiSCaO dispersion and colloidal dispersion

^[11]. The present study showed that BiSCaO Water (pH > 12.7) has microbicidal activity against various pathogenic bacteria and viruses such as both enveloped virus and nonenveloped virus. Therefore, BiSCaO Water may be valuable for the limitation of the spread of respiratory viruses such as COVID-19, although it is necessary to study additional microbicidal/virubicidal activity including coronavirus SARS-CoV-2.

. The present study showed that BiSCaO Water (pH > 12.7) has microbicidal activity against various pathogenic bacteria and viruses such as both enveloped virus and nonenveloped virus. Therefore, BiSCaO Water may be valuable for the limitation of the spread of respiratory viruses such as COVID-19, although it is necessary to study additional microbicidal/virubicidal activity including coronavirus SARS-CoV-2.

The article has been published on 10.3390/molecules25133001