Saccharification Rahul et al (2014), Jang et al

            Saccharification
can be done either by enzymatic or chemical method. Manns et al (2014) has
discussed about the various methods of extracting carbohydrates from seaweeds.
In this literature, the yield of carbohydrate by using different acid
hydrolysis treatments or the cellulase treatment is described. Cellulase
treatment is also described by Cho et al (2014).

Yaich et al (2014)
has reported different fractions of galactose by acid hydrolysis and enzymatic
treatment on Ulva lactula. In this
procedure, HCl is used at temperatures 80 ºC and 90 ºC and at pH 1.5 and 2. Protease
is also used to extract the carbohydrates and the results are compared. By acid
treatment, about 0.59 to 0.63 % of galactose have been extracted and the
protease enzyme has separated 0.76 % of galactose.

Markou et al (2013)
has investigated the saccharification process in algae using the acids H2SO4,
HNO3, HCl and H3PO4. Each acid was taken in four
different concentrations (0.25 N, 0.5 N, 1 N and 2.5 N) and for each
concentration the hydrolysis was conducted under four temperatures (40 °C, 60
°C, 80 °C and 100 °C). The lowest acid concentration has produced good results.

Yoon
et al (2010) has studied the effect of acid concentration in extracting
monosugars from the red seaweed, Gelidium
amansi. Here, sulphuric acid is used at different percentages to produce
bioethanol.

Tiwari
and Troy (2015) have discussed about the different methods of chemical extraction
of carbohydrates from brown seaweeds. Venkatesan et al (2017) have also explained the same but by different chemical
methods.

Chirapart
et al (2014) has reported the use of
2N HCl at 100 ºC for 15 hours. Since the duration is very long, it could result
in evaporation of the extract. Therefore, with few modifications in the
procedure detailed by Jang et al (2013), the extraction of monosaccharide was
proceeded. HCl was used instead of H2So4 to avoid the
formation of sulfated groups.

            Analysis of the extract was done by
High Performance Liquid Chromatgraphy (HPLC) as guided by the works of Jang et
al (2013), Chirapart et al (2014) and Templeton et al (2012).

Similarly,
in order to find the complete composition of the extract, Gas Chromatography –
Mass Spectrometry (GC-MS) has been done in the literatues Rahul et al (2014), Jang
et al (2013), Rodeiro et al (2015) and He et al (2016).

The galactose fraction from the extract can be separated
by ion exchange chromatography as mentioned in Rodrigues et al (2011), Shanti
et al (2014) and Mahendran and Saravanan (2013).

            D- tagatose is a low calorie sweetener with low glycemic index. The properties
of this sugar were studied by Kavamura (2004). Meanwhile, the proposed levels
of D-tagatose in various foods have also been reported in this article.

            D-
tagatose is an isomer of galactose. It can by produced by the isomerisation of  galactose by the enzyme L- arabinose
isomerase. This was reported by Staudigl et al (2014) and Wanarska and Kur
(2012). Here, the separation of galactose from milk and milk products and its isomerisation
by the enzyme L- arabinose isomerase has been explained.