Enzyme activities in waste lyophilizate
Generally, SM grows slowly and takes 2.5–3 times longer to fruit compared with MHM and OM. Fruit bodies of SM were harvested three times during the 174 culturing days. Among the three waste preparations of SM, the last waste showed the highest activities of all the enzymes investigated; the first and second extracts had weaker polysaccharide hydrolase activities.
A comparison of polysaccharide hydrolase activities in shochu lees media waste of MHM, OM and SM (after the third harvest) and conventional media waste of MHM and OM is shown in Table 1. Different enzymes had the different pH optima; in our experiment, pH 5.0 was the most common and was selected for enzyme assays.
The enzyme profiles of the three waste extracts differed: MHM preparations displayed the highest activity towards AZCL-substrates such as HE-cellulose, β-galactomannan, and arabinoxylan. In OM preparations, α-amylase and arabinanase showed the highest activity, and β1,3-glucanase activity was comparable with that of the activity measured in MHM preparations. Enzyme activities from MHM and OM in the conventional media containing sawdust and rice bran were lower than those in the shochu lees medium. Schimpf and Schulz (2016) reported that SM medium showed higher cellulase and xylanase activities than MHM. However, Table 1 shows both enzyme activities in the shochu medium of MHM are higher than SM medium. It is evident that mushroom cultivation waste medium of shuchu lees is better as the additive of animal feed.
Sudo et al. (2008) reported glycosidase activities in MHM media with α-galactosidase activity being the highest of all the glycosidases measured. The glycosidase activity profiles differed among the strains used and it is probable that profiles of polysaccharide hydrolyses activities differ among the strains in one mushroom species.
Digestion of feedstuffs by waste lyophilizates
Amylase-digested NDF contains polysaccharides and lignin that are sometimes difficult for domestic animals, such as heat-stressed cows, to digest. A decrease in NDF in feedstuffs after treatment with mushroom waste extracts could increase the nutritional efficiency. The enzyme preparations listed in Table 1 were used in the hydrolysis of NDFs. Table 2 shows the NDF content after enzyme treatment.
MHM and OM waste had comparable effects on NDF. The decrease in NDF was the highest in sweet potato runner. Poaceae plants such as Italian ryegrass and rice contain silica, and sweet potato contains more hemicellulose (Cornnelissen and Thompson 1997, Pauly and Keegstra 2008, Vogel 2008). Consequently, it can be inferred that sweet potato runner NDF was most hydrolyzed by MHM extract. The hydrolysis of Italian ryegrass NDF was small (Table 1). Therefore, to confirm the hydrolysis, ten times the amount of extract was used. NDF decreased to 272 and 268 mg/g, by MHM waste and OM waste treatment, respectively. Thus, it was proved that waste enzyme treatment on feedstuffs is effective.
Changes in sugar composition of NDF
Table 3 summarizes the changes in sugar composition of NDF after waste enzyme treatment. The amount of sugar was higher in the Italian ryegrass treated with SM waste than in the untreated (control) and MHM treated groups (Table 2).
The NDF content of Italian ryegrass decreased after SM waste treatment. If there had been equal degradation of sugar and lignin, the sugar ratio compositions would have been unchanged between the treated and control groups. The amount of sugar in the NDF was increased, suggesting that the degradation of lignin preceded the degradation of polysaccharide during the initial stages of SM waste treatment. Leatham (1985) reported that during SM growth, lignin was degraded faster than polysaccharides; however, lignin degradation activity was still observed during the final stages of growth. After the treatment with MHM waste, there was a notable decrease of xylose in the NDF of rice straw, and large decreases in glucose and xylose were observed in sweet potato runner NDF. These results suggest that the addition of enzyme preparations effectively improves the digestibility of some feedstuffs.
Takabatake et al. (2016) reported that the addition of polysaccharide-degrading enzymes into sawdust-based culture media containing Hericium erinaceus and Pholiota microspora efficiently increased the fruiting body yield. These results depend on the profiles of enzyme which mushroom secrete being different. We suggest that further improvement on feedstuff digestibility will be possible based on a combination of enzyme preparations from MHM and SM or MHM and OM.
All of the antioxidant activities were lower in the waste media than in the fruit bodies. Figure 1 shows the antioxidant activities of waste media. Scavenging activities in MHM and OM waste media were lower than in the start media (media before spawn inoculation), irrespective of medium composition.
SM antioxidant activity was the highest of the mushrooms examined, especially in the shochu lees waste after the second harvest. Floegel et al. (2011) reported DPPH scavenging activity of many foods were lower than 100 trolox unit/g.
In the similar manner, SOD activity was in the range of 50–400 SOD unit in the media for SM, OM, and MHM, though we found around 1500 SOD activity in fruit bodies of OM. Previously, Niwa and Sasaki (2003) reported that SOD activity was around 200 in leaves of Japanese cedar. These results indicate that SOD activity in the mushroom cultivation waste media is normal.
Taken together, antioxidant activity was judged to be not so high in the mushroom waste medium.