Beverage ethanol production via fermentation is an age long tradition in many parts of the world. In the tropical world and elsewhere, indigenous people are involved in the entire value chain of traditional alcohol fermentation. Jespersen (2003) reported that most beverages and foods in Africa are produced at household level or on small industrial scale often of varying qualities. Aiyeloga et al. (2014) reported the potentials of raffia palm wine in sustaining livelihood in rural and urban populations in Nigeria. However, in Africa, Asia and South America, there has been an increasing incidence of methanol contamination in traditionally fermented alcoholic drinks (WHO 2014). Several cases of methanol poisoning have been reported in India and elsewhere. For instance in 2008, over 180 persons were killed in Bangalore and in 2009, 138 were killed in Gujarat, India. In 2015, 27 persons died in India after consuming toxic ethanol. In 2009, 25 persons died in Indonesia after consuming fermented palm wine containing methanol. About 130 persons died in some India villages in 2011 linked to poisonous ethanol consumption. In Czech Republic, 127 persons were poisoned from contaminated alcohol, out of which 42 died (Vaskova 2013). In 2014, the World Health Organization (WHO) alerted that there have been increasing outbreaks of methanol poisoning in several countries including Kenya, Gambia, Libya, Uganda, India, Ecuador, Indonesia, Nicaragina, Pakistan, Turkey, Czech Republic, Estonia and Norway. The size of these outbreaks ranged from 20 to over 800 victims, with case fatality rates of over 30 % in some cases (WHO 2014). Lachenmeier et al. (2011) evaluated the risk of contaminated unregulated alcohol in the European Union.
In Nigeria, between April and June 2015, a total of 89 persons died following the consumption of locally produced ethanol beverage called kaikai/ogogoro/apeteshi or illicit gin. Kaikai is produced mostly from the sap of raffia palm and oil palm and to a lesser extent from other palms such as date palm, nipa palm etc. Laboratory analysis carried out by WHO and NAFDAC (National Agency for Food, Drug Administration and Control) show that the beverage contain 16.3 % methanol, while the blood methanol concentration of victims was found to be 1500–2000 mg/l. Victims exhibited symptoms of methanol poisoning including loss of consciousness, dizziness, weakness and breathing difficulties, blurred vision and blindness, weight loss, headache, abdominal pains, nausea, diarrhea and vomiting (Methanol Institute 2013). WHO (2014) reported that blood methanol concentration above 500 mg/l is associated with severe toxicity, whereas concentration above 1500–2000 mg/l causes death in untreated victims. While investigation is ongoing on the source/origin of methanol in the beverage, the Federal Government of Nigeria (FGN) placed a ban on the production, sale, distribution and consumption of locally fermented beverage in Nigeria. Enforcement of the ban was heightened in the months (June–August 2015) following the incidence, but as of the time of writing (November 2015) enforcement has slacked. But the ban on the age long fermentation processes could have major impacts on the local economy. For instance, over 50 million people consume palm wine in Southern Nigeria (Obahiagbon 2009).
Raffia palm, which is among the most diverse and geographically widespread palm, is found in Africa, Asia and South America (Oduah and Ohimain 2015). The palm has many potential uses (Oduah and Ohimain 2015) but it is currently undertilized (Ohimain et al. 2015). Production of beverage ethanol from raffia palm provide a source of employment especially for rural people (Obahiagbon and Osagie 2007; Ohimain et al. 2012). Aiyeloja et al. (2014) studied the potential of raffia palm in the sustenance of rural and urban population in Nigeria. They found that raffia palm beverage value chain provides profit of ₦50,000–₦90,000 ($ 1 = ₦220) to producers and ₦45,000–₦70,000 to marketers. The complete ban on traditionally fermented beverages could be detrimental to the country’s economy especially at a time when most economics are under recession, with high inflation and un-employment rates. Nigeria is currently experiencing an economic downturn due to low crude oil prices. Hence, there is the need to establish the source/cause of methanol in traditionally fermented alcoholic beverages. Methanol Institute (2013) reported that methanol is often deliberately added to alcoholic beverages by unscrupulous and illegal criminal enterprises as a cheaper alternative to the production of cheaper ethanol. This may be unlikely in Nigeria and many other developing countries where methanol is not domestically produced but imported at costs higher than the cost of alcoholic beverage. For instance, domestically produced ethanol (40–60 % alcohol content) is quite cheap costing ₦20 per shot of 30 ml i.e. ₦670/l as against ₦5168/l of 99.85 % methanol (excluding importation and duty costs). Hence, there is need for research to focus on other possible sources of methanol in locally fermented beverages. WHO (2014) reported that outbreaks of methanol often occur when methanol is added to alcoholic beverages. Ohimain et al. (2012) reported that alcoholic beverages are produced in Nigeria using rudimentary equipment under spontaneous fermentation, which lacked effective controls and are carried out by uneducated rural workers with poor hygiene in an unsterile environment. Traditional fermentation is carried out by mixed cultures consisting of yeast, other fungi and bacteria. Though, most of the traditionally fermented food and beverages are dominated by the yeast Saccharomyces cerevisiae, and to a lesser extent Lactobacillus (Jespersen 2003; Ogbulie et al. 2007; Karamoko et al. 2012; Rokosu and Nwisienyi 1980), the presence of other microbes can lead to the production of diverse products including methanol (Dato et al. 2005; Shale et al. 2013; Kostik et al. 2014). Several compounds could be produced during mixed fermentation with several organisms. Also, it has been severally reported that microbial fermentation of substrates rich in pectin can result in the formation of methanol (Nakagawa et al. 2000; Mendonca et al. 2011; Siragusa et al. 1988). Contaminating yeast has been demonstrated to produce methanol during traditional fermentation (Dato et al. 2005). Recent studies have also shown that the ethanol fermenting yeast, S. cerevisiae has several strains with slightly different metabolism (Jespersen 2003; Stringini et al. 2009; Okunowo et al. 2005) with some strains possibly producing methanol. More worrisome are recent studies showing increase in blood methanol level in some persons even after consumption of methanol-free ethanol (Shindyapina et al. 2014; Dorokhov et al. 2015). These authors recognized two sources of methanol in human systems, endogenous and exogenous sources. It is generally believed that unscrupulous vendors deliberately spike beverages with methanol in order to increase the alcohol content. The aim of this review is to present alternative viewpoint showing the possible role of microbes in the production of methanol in traditionally fermented beverages. We reviewed literature on traditionally fermented alcoholic beverages, assessed the methanol content of the beverages, the pectin content of their feed stocks and the microbial species involved in the fermentation in an attempt to establish a possible role of microbes in the production of methanol in traditionally fermented alcoholic beverages.
(To be Continued for next month)