Lower concentration of glucose was often obtained from enzymatic hydrolysis process of agricultural residue due to complexity of the biomass structure and properties. High substrate load feed into the hydrolysis system might solve this problem but has several other drawbacks such as low rate of reaction. In the present study, we have attempted to enhance glucose recovery from agricultural waste, namely, “sago hampas,” through three cycles of enzymatic hydrolysis process. The substrate load at 7% (w/v) was seen to be suitable for the hydrolysis process with respect to the gelatinization reaction as well as sufficient mixture of the suspension for saccharification process. However, this study was focused on hydrolyzing starch of sago hampas, and thus to enhance concentration of glucose from 7% substrate load would be impossible. Thus, an alternative method termed as cycles I, II, and III which involved reusing the hydrolysate for subsequent enzymatic hydrolysis process was introduced. Greater improvement of glucose concentration (138.45 g/L) and better conversion yield (52.72%) were achieved with the completion of three cycles of hydrolysis. In comparison, cycle I and cycle II had glucose concentration of 27.79 g/L and 73.00 g/L, respectively. The glucose obtained was subsequently tested as substrate for bioethanol production using commercial baker's yeast. The fermentation process produced 40.30 g/L of ethanol after 16 h, which was equivalent to 93.29% of theoretical yield based on total glucose existing in fermentation media.

Sago wastewater which contains starchy fibres from sago starch processing mills is commonly discharged directly to nearby stream thus contribute to serious environmental pollution. Sago fibre which is known to be a local agricultural waste mainly contains residual starch of about (50 – 60 %) together with cellulosic component. These contribute to high carbohydrate contents which suitable to be used as substrate for ethanol production. Initially, sago fibre (SF) was converted into sago fibre hydrolysate (SFH) via enzymatic hydrolysis using commercial enzymes; Liquozyme SC DS and Spirizyme Fuel HS. This study emphasized on batch ethanol fermentation by commercial baker’s yeast utilizing 50 g/L and 80 g/L glucose of SFH as the sole fermentation medium. The results indicate that 50 g/L glucose from SFH media is capable of generating maximum ethanol concentration at 20.33 ± 0.15 g/L, with highest glucose consumption efficiency (97.78 %) during 24 hours of fermentation. Similar concentration of bioethanol was obtained in 50 g/L glucose of commercial glucose (CG) media which is at 20.04 ± 0.06 g/L. However, lower ethanol concentration was obtained in both 80 g/L glucose from SFH (13.32 ± 0.12 g/L) and CG (12.98 ± 0. 04 g/L media), respectively. Addition of yeast extract at 3 g/L into 80 g/L SFH as well as CG significantly improve ethanol fermentability (SFH: 41.04 ± 0.04 g/L and CG: 33.96 ± 0.04 g/L). Based on statistical analyses, 50 g/L glucose of SFH media exhibit the highest ethanol yield (0.42 ± 0.003 g/g) and highest fermentation efficiency (81.35 ± 0.572 %) compared to 80 g/L glucose (0.24 ± 0.008 g/g; 46.65 ± 1.50 %). Conclusively, this study demonstrated that glucose in SFH was metabolized efficiently by commercial baker’s yeast during ethanol fermentation, thus suggesting the capability of SFH to be a feasible and alternative substrate with less expensive nitrogen source for the renewable bioethanol production.

This study was carried out to examine the effects of sago bark (SB) and sago frond (SF) waste on the growth and yield of grey oyster mushrooms (Pleurotus sajor-caju). Nine substrate formulas were studied, including sawdust (SD) alone as a control and the combination of 25:75, 50:50, and 75:25 ratios between SD and SB or SF. The results showed a significant difference in the total colonisation period, total fruiting body yield, and biological efficiency (BE). However, an insignificant difference was determined in the characteristics of the fruiting body for different substrate formulas. The substrates with the ratio of 50SD:50SF and 100 SD are the most suitable substrate formulas for the cultivation of P. sajor-caju. One hundred (100) SD achieved the fastest total colonisation period (24.44 days) but there was no significant difference with 75SD:25SF (24.78 days) and also obtained the fastest first harvest (50.33 days). However, 100SD produced a significantly lower total fruiting body yield (77.99 g/bunch) compared to 50SD:50SF, which produced the highest total yield (88.09 g/ bunch) and highest BE (17.62%) with a short total colonisation period (26.45 days). The substrates produced high values in cap diameter, stipe length, and effective fruiting bodies.

In Malaysia, sawdust is widely used as a substrate for the cultivation of grey oyster mushrooms (Pleurotus sajor-caju). Due to the scarcity and increasing cost of sawdust, this research investigated the feasibility of employing sago hampas as an alternative substrate for the cultivation of P. sajor-caju. In Sarawak, sago hampas were discarded into the river together with wastewater or incinerated, causing water and air pollution. In this study, P. sajor-caju was grown in five different formulations which are 100% sawdust (100SD) as control, 100% sago hampas (100SH), 75% sawdust + 25% sago hampas (75SD:25SH), 50% sawdust + 50% sago hampas (50SD:50SH), and 25% sawdust + 75% sago hampas (25SD:75SH). The substrate was mixed with rice bran and calcium carbonate at a dry matter basis in the ratio of 100:10:1. For the biological efficiency, 50SD:50SH recorded the highest yield (115.07%) compared to singular substrate 100SD (19.52%) and 100SH (37.04%). The higher lignin content and moisture-holding capacity in 100SD might not give better physical characteristics of P. sajor-caju. At the end of the study, supplementation sawdust with sago hampas especially formulation 50SD:50SH is recommended as the best formulation to reduce sawdust and utilise sago hampas as an alternative substrate for P. sajor-caju.