Solid state fermentation of maize (Zea mays) cob by Pleurotus ostreatus strain EM-1: Biopolymer profiles and cellulose degradability

The low digestibility and low protein content of maize cob are major limitations to its use as animal feed in Ghana. The possibility of enhancing the feed potential of maize cob through solid state fermentation byPleurotus ostreatus strain EM-1 was investigated. At the end of spawn run, lignin, cellulose and hemicellulose content had decreased by 42.3, 5.6% and 41.0% respectively. No further reduction in lignin content occurredthereafter. In contrast, after 28 days, cellulose and hemicellulose had been degraded by 36.0% and 58.5% respectively. A biphasic protein profile, characterized by a 6-fold increase by day 14, followed by a dramatic decline was observed. The rate of release of reducing sugars from spent maize cobs during incubation with exogenous cellulase was 400% greater than that of untreated maize cobs. The present findings indicate that the positive effects of P. ostreatus strain EM-1 on the nutritive value of maize cob appear to be optimal after complete colonization by mycelia. At this stage, maximum biodegradation of lignin had occurred, protein content was markedly elevated and the reduction in cellulose content was negligible. Thus, solid state fermentation by Pleurotus ostreatus strain EM-1 may be an efficient means of transforming maize cob into nutritive animal feed. Keywords: Oyster mushroom, delignification, animal feed, biodegradation, cellulose, hemicellulose

Differentiation of Two Pleurotus Species Based on the Restrictive Digestion Profile of the Internal Transcribed Spacer Region

Two oyster mushrooms (Pleurotus eous P-31 and P. ostreatus EM-1) are under either cottage industry or semi-commercial cultivation in Ghana. The latter (P. ostreatus) is already well known to the public and on the shelf of some leading supermarkets. There is morphological resemblance between the two species making it difficult for the untrained eye to distinguish between them except for the colour difference. In this study, molecular methods were em­ployed to differentiate among the two species. The Internal Transcribed Spacer ITS 1 and ITS 4 regions of the rDNA of the two oyster species were amplified by the conventional PCR using the universal primer pair, ITS 1 and ITS 4 followed by restrictive digestion with enzymes, (Hh I, Hinf I, Rsa I and Hae III). The two species could not be separated based on the ampli­fied bands only, as both produced a characteristic band size of 650 bp. Gel profiling showing restrictive patterns generated by the four enzymes indicated that only the Hae III restrictive enzyme was effective in separating P. eous P-31 and P. ostreatus EM-1. This is the first record of the separation of the Ghanaian Pleurotus species by molecular methods indicating their genetic differences

Human Enteroviruses isolated during acute flaccid paralysis surveillance in Ghana: implications for the post eradication era

Introduction: Surveillance of acute flaccid surveillance (AFP) has been used world-wide to monitor the control and eradication of circulating wildpolioviruses. The Polio Laboratory since its accreditation in 1996 has supported the Disease Surveillance Department for AFP surveillance. Thisstudy aims to isolate and characterize human enteroviruses from patients with AFP in Ghana. Method: Stool suspension was prepared from 308samples received in 2009 from the surveillance activities throughout the country and inoculated on both RD and L20B cell lines. Isolates thatshowed growth on L20B were selected for real-time RT-PCR using degenerate and non-degenerate primers and probes. RD isolates were however characterized by microneutralisation technique with antisera pools from RIVM, The Netherlands and viruses that were untypable subjected toneutralization assay using antibodies specific for E71. Results: Of the 308 samples processed, 17 (5.5%) grew on both L20B and RD cells while 32(10.4%) grew on RD only. All 28 isolates from L20B were characterized by rRT-PCR as Sabin-like polioviruses. No wild poliovirus or VDPV wasfound. However from the microneutralisation assay, six different enteroviruses were characterized. Among these, Coxsackie B viruses were most predominant followed by Echovirus. Three children from whom non-polio enteroviruses were isolated had residual paralysis while one child with VAPP found. The non-polio enteroviruses circulated throughout the country with the majority (20.7%) from Ashanti region. Conclusion: Thisstudy showed the absence of wild or vaccine-derived poliovirus circulation in the country. However, the detection of three non-polio enterovirusesand one Sabin-like poliovirus with residual paralysis call for continuous surveillance even in the post polio eradication era

Characterization of the dominant microorganisms responsible for the fermentation of dehulled maize grains into nsiho in Ghana

Nsiho (white kenkey) is a type of kenkey, a sour stiff dumpling, produced from fermented maize meal in Ghana. The dominant microorganisms responsible for the fermentation of nsiho were characterized by analysing samples from four traditional production sites at Anum in the Eastern Region of Ghana. During 48 h of steeping dehulled maize grains, the pH values decreased from 6.05 to 5.93 to 3.59 to 3.55, whilst titratable acidity increased from 0.02 to 0.03 to 0.27 to 0.32%. In the subsequent 12 h dough fermentation, the pH decreased from 6.02 to 5.80 to 3.52 to 3.46, whilst titratable acidity increased from 0.25 to 0.27 to 0.35 to 0.38%. The lactic acid bacteria population increased by 2 to 5 log units to concentrations of 107 to 108 CFU/ml during steeping and by 2 to 3 log units from 105 to 106 CFU/g to 108 to 109 CFU/g during dough fermentation. Yeasts counts increased by 3 to 4 log units during steepingand by 2 to 4 log units during dough fermentation. The most frequently isolated lactic acid bacteria responsible for nsiho fermentation were identified as Lactobacillus fermentum (47.1%), Lactobacillus brevis (25%), Lactobacillus plantarum (14.42%), Pediococcus pentosaceus (8.65%) and Pediococcus acidilactici, (4.8%). The dominant yeasts species were Saccharyomyces cerevisiae (47.6%), Candida krusei (29.1%),  Debaryomyces spp., (15%) and Trichosporon spp., (8.3%). This is the first  study to report on the micororganisms involved in nsiho fermentation.Key words: Nsiho, dehulled maize, kenkey, lactic acid bacteria, indigenous African fermented foods

Effectiveness of three different storage structures and curing process for the storage of sweet potato (Ipomoea batatas) in Ghana

Three different storage structures and two curing processes for the storage of sweet potato (Ipomoea batatas) were studied at the CSIR-Food Research Institute, Accra. Sweet potato roots initially cured under warm(30-35 °C) and very humid (90-95% relative humidity) conditions for 7 and 14 days were stored in local (traditional), pit, and clamp storage structures for 84 days. After 0-84 days of storage, the roots were sampled and physically assessed into wholesome, sprouted, fungalinfected, and insect and rodent-damaged. The decrease in percentage wholesome roots corresponded to an increase in percentage fungal-infected roots from 0 to 84 days of storage in all the three different storage structures. Clamp storage structure recorded the highest percentage wholesome roots (20.0%) compared to pit (16.3%) and local (0%) after 84 days of storage when roots were cured for 7 days. However, for 14 days cured roots stored for 84 days, local storage structure recorded the highest percentage wholesome roots (20%), pit (0%), and clamp (10%). Higher percentages of fungal-infected sweet potato roots were recorded from roots cured for14 days. Percentage sprouted roots was higher in clamp, followed by pit and local storage structures. Sprouting was delayed for sweet potato roots that were cured for 14 days in all the storage structures. Percentage damage of sweet potato roots by insect and rodent was lower inall the three storage structures compared to the fungalinfected sweet potato roots

Comparison of the microbial composition of African fermented foods using amplicon sequencing

Fermented foods play a major role in the diet of people in Africa, where a wide variety of raw materials are fermented. Understanding the microbial populations of these products would help in the design of specific starter cultures to produce standardized and safer foods. In this study, the bacterial diversity of African fermented foods produced from several raw materials (cereals, milk, cassava, honey, palm sap, and locust beans) under different conditions (household, small commercial producers or laboratory) in 8 African countries was analysed by 16S rRNA gene amplicon sequencing during the Workshop “Analysis of the Microbiomes of Naturally Fermented Foods Training Course”. Results show that lactobacilli were less abundant in fermentations performed under laboratory conditions compared to artisanal or commercial fermentations. Excluding the samples produced under laboratory conditions, lactobacilli is one of the dominant groups in all the remaining samples. Genera within the order Lactobacillales dominated dairy, cereal and cassava fermentations. Genera within the order Lactobacillales, and genera Zymomonas and Bacillus were predominant in alcoholic beverages, whereas Bacillus and Lactobacillus were the dominant genera in the locust bean sample. The genus Zymomonas was reported for the first time in dairy, cereal, cassava and locust bean fermentations