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There are various kinds of substrate can be used to produce biohydrogen and biomethane
pass through anaerobic dark fermentation process, for example, monomeric sugars (Ren et al.,
2009; Mangayil et al., 2011), sucrose (Hussy et al., 2005; Lin et al., 2006; Perera and
Nirmalakhandan, 2010; Perera and Nirmalakhandan, 2011), Lactose (Calli et al., 2008; Davila-
Vazquez et al., 2008; Rosales-Colunga et al., 2012), cheese whey (Kargi et al., 2012; Rosales-
Colunga et al., 2012; Perna et al., 2013; Rosa et al., 2014), starch (Argun and Kargi, 2010; Cakır
et al., 2010; Xia et al., 2014). However, the usage of pure sugars is only for trying to understand
the microbial physiology of hydrogen production since it’s too expensive for use as substrate in
an industrial scale. Thus, researchers are interested to produce biogas from wastewater generated
from several industries due to their low costs and direct treatment of wastewater with bioenergy
is profitable. Resulting, extensive research has been used wastewater generated from several
industries including wastewater generated from food and beverage industries, waste sludge from
wastewater treatment plants, mostly include slaughter house and meat-processing, daily
industries, fish processing, starch processing, edible oil, olive mill, beverage and distilleries, fruit
and vegetable processing. Moreover, wastewater generated from concentrated latex (Perrella and
Gaspari, 2002; Abraham et al., 2009; Santipanusopon and Riyajan, 2009; Kongkaew et al.,
2012) and wastewater generated from palm oil mill factories (O-Thong et al., 2008; Ismail et al.,
2010; Alrawi et al., 2011; Fang et al., 2011; Khemkhao et al., 2012) have been successfully used
to produce biohydrogen and biomethane by anaerobic dark fermentation.
Skim latex serum (SLS) is a by-product generated from concentrated latex production
process by centrifugation method. This process about 10% of rubber materials lost as a by-
product, however, it able to recover rubber by using 98% sulfuric acid. Nevertheless, rubber
materials are recovered using 98% sulfuric acid, but skim latex serum is still remaining mainly
nutrients, including carbohydrates, proteins, lipids, sugars and carotenoids. However, the
microorganisms can be used these nutrients to growing (Santipanusopon and Riyajan, 2009;
Abraham et al., 2009). Normally, the concentrated latex production process, ammonia (NH 3),
zinc oxide and tetramethylthiuram disulfide (ZnO/TMTD) and sulfuric acid (H 2SO 4) was added
to preservation and coagulation of latex (Perrella and Gaspari, 2002; Rippel et al., 2003;
Santipanusopon and Riyajan, 2009). However, some of these chemical reagents are remaining in
the skim latex serum which important to the microorganisms growing and also affecting to the
efficiency of biogas production. Raw skim latex serum is acidic yellowish fluid consisting of
chemical oxygen demand (COD) ranged 29.2 – 35.8 g/L, total Kjeldahl nitrogen (TKN) ranged
4.9 – 5.1 g/L, carbohydrate content ranged 379 – 603 mg/L and protein content ranged 6.4 – 7.6
g/L (Kongjan et al., 2014; Sama et al., 2014). Skim latex serum is a concentrated substrate with
high concentrations of COD and TKN, resulting in low C/N ratio around 7 which are still
limitations substrate used for biogas fermentation. Corresponding with a study from Kongjan et
al. (2014) found that a relatively low of hydrogen production yield achieved from sole
fermentation of skim latex serum was 59.2±2.4 mL H 2/g-VS, which is just only 11% of hydrogen
theoretical yield (498 mL H 2/g-VS). They were reported the possible reason for having low
hydrogen formation because the competition of hydrogen producing bacteria and sulfate